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  1. Was having problem with no air forced coming through ducts
    in bedroom. Removed furnace to clean and check for duct blockage.
    Found medal tape had fallen off and was restriction flow. Fixed that
    problem, cleaned fan and reinstalled furnace. Hooked everything back
    up except the thermostat wired. Learned long ago to jump the wires out at
    the furnace and check it before closing the compartment. Worked fine. Finished
    hooking everything up and closed compartment. Turned on thermostat and NOTHING
    worked. No heat, a/c or fan. Pulled the thermostat, took off the furnace
    thermostat wired and hooked them together. Furnace worked. Haven’t finished trouble
    shootong the thermostat yet. Long process for a solid state thermostat with a/c,
    fan and furnace all on one thermostat. Even with furnace wires disconnected,a/c
    and fan will not work. Seems 12 vdc comes through furnace. Any sugestions? What
    little troubleshooting I have done, nothing makes sense. HELP!!!

    Comment by Charles — February 5, 2007 @ 3:29 am

  2. Hi Charles- the first thing I would look at is which wire hooked to which from the furnace to the thermostat.
    One thermostat wire out of the furnace will be “hot” (+12v), and if it is not hooked to the correct thermostat lead, the thermostat will not have 12 volt power to operate.

    Comment by Chris — February 5, 2007 @ 10:00 am

  3. I use a heat pump/propane furnace. In this weather the heat pump always works but when it is colder the propane comes on and a blue light on my colemane revcon thermostat comes on. Lately a red light has been coming on. It says emg above it. It stays on and circulates the air to keep temp stable but is just blowing air. no heat. Any ideas?

    Comment by Jean — March 24, 2007 @ 10:02 pm

  4. Hi Jean,
    I hate to say it, but I am unfamiliar with that type of thermostat in an RV, and cannot find any information about it on the Coleman website (or in my service documents).

    — Chris

    Comment by Chris — April 9, 2007 @ 3:09 pm

  5. HI CRIS,

    Comment by BOB — September 9, 2007 @ 7:18 pm

  6. My father-in-law has a 37’5th wheel forgot the model? but it has a sububan lp furnace.We had it going and worked well but after we brought it to his lot now the pilot would not stay lit.After some investigating found a bees nest in the exhaust.We pulled it out with a bent clothes hanger then blew it out with air.Now it wont stay lit at all

    Comment by bob — October 19, 2007 @ 12:38 pm

  7. Hello,
    My propane furnace will not keep the pilot light lit after it is finished running. It will make a click sound and the pilot will go out. I just changed the thermocouple two days ago and it did not solve the problem. Any insight will be greatly appreciated. Thanks,

    Comment by J — November 11, 2007 @ 6:34 pm

  8. Hi Jeffrey,
    A couple of things to check- the pilot assembly may need to be cleaned, and sometimes if the pilot is set too high, it will starve for oxygen just after the burner shuts off, and go out. The flame should *just* envelope the end of the thermocouple.
    But.. in some furnaces it is near impossible to actually see the pilot flame.

    — Chris

    Comment by Chris — November 14, 2007 @ 5:35 pm

  9. I’ve got an old coleman 4225A furnace in a 1976 Winnie. Was running great until this fall(deer season). It is burning very rich, soot coming out of exhaust and too hot in heat exchanger. Pulled unit to check for any blockage or obstructions. None found. Both fans working well, just replaced the motor two years ago. Can’t adjust for a good blue flame as before. Very tall flame too tall, which starts out blue but too much yellow. Could it be an air leak or has the General Control 4225A809 gas valve gone bad? Gas stove and frig work okay, which I think leaves out main gas regulator.

    Comment by Joe Pazzelli — November 15, 2007 @ 2:03 pm

  10. Hi Joe,
    Generally that is sign of either too much fuel or too little air. Did it run OK after the motor change? If the motor was running backwards, it would still work, but not put enough airflow through. Likewise the combustion blower wheel could be installed wrong.
    If I recall correctly, that unit has a cast iron burner- the slots in those burners are very prone to blockage by rust, which blocks the air flow as well.


    Comment by Chris — November 15, 2007 @ 7:35 pm

  11. Thanks Chris.
    The unit ran fine after the motor change out, good clean blue normal size flame on all three burner sections. It does have a cast iron burner. I’ll check for blockage there. The only other thing is can I still get a gas control valve for this unit or will I have to replace the furnace?

    Comment by Joe Pazzelli — November 16, 2007 @ 1:24 pm

  12. Hi Joe,
    I really don’t think the gas valve is the problem- I would bet on the slots in the burner being plugged up.
    It’s been a while since I services one of these, but I *think* that the slots are wide enough that they can be cleaned with a hack saw blade- you don’t want to make the larger, just clean them out.

    — Chris

    Comment by Chris — November 17, 2007 @ 7:41 pm

  13. Thanks Chris,
    You were right on the slots being clogged. I remember cleaning them out when I replaced the motor. Unfortunately when I put the unit back together, the pilot won’t stay lit so I’m getting a new thermocouple today; hoping to fix all my problems. As for the valve, I was told that they are no longer available. I just wanted to know if I could still get one.

    Comment by Joe Pazzelli — November 19, 2007 @ 7:33 am




    [email protected]

    Comment by margaret — November 29, 2007 @ 9:31 am

  15. Hi Margaret,
    I guess the easiest thing would be to replace the thermostat, but you might take the cover off and look for a small adjustment called an anticipator- which will be a wire with a slide connector on it. Sometimes they are a round assembly, sometimes they are straight. If you move the slider down to zero, often that will “fix” a problem like that (the wire sometimes gets corroded, and moving the adjustment can help.
    To replace it, a popular replacement is the Hunter model 42995, which is available at WalMart for about $20. It is an electronic model, but will work fine for furnace only- just hook the 2 wires to the RH and W terminals.


    Comment by Chris — November 30, 2007 @ 8:01 pm

  16. Hello, I have an Excalibur Hydroflame 8500 IV which seems to have lost it’s muscle. Everything works fine as it always has – with the exception that it doesn’t seem to heat my bus up like it used to without consuming excessive amounts of propane. I think that the flame must not be hot enough anymore but I can’t see it from any angle inside or out, I can however hear the difference if that makes sense? Every winter (this is the 5th) I acclimate to the familiar “tiger torch roar” but it is a sub-sound under the blower motor this year. Plus the air just doesn’t feel as hot as it used to coming out. From my RV repair books I think the burner/flame has issues but they don’t show how to get at the burner of this model, nor does the 3 page Atwood installation manual. Is there an easy way to determine if this is the problem? I live in the bus so leaving it at a shop is out of the question – and pulling the furnace out would have to happen while it’s snowing because it won’t be warming up here again until May… Thank you for any suggestions or directions on how to see or clean or adjust my Hydroflames Flames!

    Comment by Sherii — December 3, 2007 @ 8:38 pm

  17. Hi, I have a Coleman [High efficiency gas-fired furnaces tubular heat exchanger series Model: P*UR / G9T-UP/ FG9-up (upflow) 40 – 140 MBH input] and it seems that our furnace turns on, but shuts off after 1 or 2 minutes of heating. it seems to give 6 red flashes when i check the furnace control dignostics, and in the manual it seems that 6 red flashes mean, the pressure switch opened 4 times during the call for heat?? and we have no idea what they mean by delay on or off mode. can you help me with this problem?

    Sincerely James

    Comment by James — December 6, 2007 @ 1:12 pm

  18. I have an older Lennox forced-air furnace with a standing pilot. For days the pilot would randomly go out. I replaced the thermocouple, cleaned the orifice, and ajusted the small hood on the pilot flame opening.
    The thermocouple it sitting nicely in a strong blue flame, and once the pilot is lit it will stay lit for five or so minutes and then you can hear the solenoid release the gas valve and it closes. End of pilot.
    Any idea what this problem might be? When the furnace runs, it runs well. The gas valve just won’t stay open to keep the pilot going. I hope it’s not the gas valve.




    Comment by Michael — December 11, 2007 @ 4:04 pm

  19. Hi James,
    I’m afraid I don’t have any service information (or, for that matter, any experience ;)) with home type furnaces.

    But.. Michael- I would almost be tempted to replace the thermocouple again, as I have seen brand new thermocouples fail. They wrok using two different metals, which generate current when heated, but every now and then the junction between these metals can open up when heated.

    — Chris

    Comment by Chris — December 11, 2007 @ 4:17 pm

  20. Thanks Chris. I’ll try that. Ggrrr.

    Comment by Michael — December 11, 2007 @ 4:57 pm

  21. Hi Michael,
    One more thought- the connection of the thermocouple at the valve is actually an electrical connection- if you look at the end, the very tip is insulated from the outside of the tube by a thin insulator.
    The thermocouple should be hand tightened firmly, plus a quarter turn- if the pilot doesn’t stay lit, give it another quarter turn. Over tightening can crush the small insulator.

    — Chris

    Comment by Chris — December 11, 2007 @ 6:15 pm

  22. Hey Chris,
    Just bought a used RV, suburbane furnace. have got it to light off twice in two weeks of trying every day, 6-7 times a day. Removed furnace, removed board took it to RV repair shop, board tested ok. I get fan, I get spark, just not lighting the pilot.

    Comment by Ron Bennington — December 17, 2007 @ 3:39 pm

  23. I have a Suburban SF-30 in an Outback 33′ that is 1.5 years old and on it’s second cool season. It always seemed to a little temperamental when igniting but has generally been trouble free. Today, not so. Everything starts and runs but no ignition takes place. Coincidentally, I had a tank switchover take place about the same time it quit. The switchover appeared to be normal as I have gas at the stove, frig, and hot water heater. I broke the line at the heater and have it there as well. Both tanks share a common regulator on the output of the switch. As for correct pressure, I don’t have a manometer but judging from the stove burners, it looks okay. ( Side question, just how much of a pressure drop can a furnace stand before it refuses to work??) Could the switchover have starved the furnace and damaged a gas valve or something? Because of it’s location, it appears that it has to be completely removed to service the components so I don’t want to do that unless absolutely necessary. Any input to a possible solution would be appreciated. Thanks.

    Comment by Kenny — December 30, 2007 @ 5:22 pm

  24. I have the exact situation as Kenny above blower blows plenty of propane, igniter tries three times but will not fire furnace. Please comment, ASAP I’m getting cold.

    Comment by rick — January 2, 2008 @ 11:59 pm

  25. Well let’s make that 3 of us, I have 05 TT with a suburban sf30f, stove work great, blower comes on then 3 or 4 popping sounds then the blower shuts off(this is in about 10 time span)…I going to wally world and buy a radiator heater

    Comment by john — January 3, 2008 @ 9:50 pm

  26. Make that four of us. I have a Suburban furnace that’s be working intermittently. Now it won’t work correctly. The fan comes on, I hear the igniter, smell the propane, but no ignition.

    Comment by glen — January 6, 2008 @ 10:55 pm

  27. For the guys up above:

    Unlikely this could help all of you but may be of help so I offer it up – I had a similar problem with my furnace last year that was due to an overfilled propane tank. Electronic lockout can occur if the gas pressure coming is too high, it’s a built in safety feature. Another similar situation my first year way back was flies and spiders camping on the burner – they clog the combustion process – after I got it lit a dozen times or so (each time it stayed on a few seconds longer) they were burnt off and I had no problems.

    Good Luck!

    Comment by FurnaceGirl — January 7, 2008 @ 3:23 am

  28. FurnaceGirl,
    Thanks, but no bugs in the burner and I’ve tried with two different propane tanks – one about 1/5 full and the other full (well, “OPD” full).

    Comment by glen — January 7, 2008 @ 10:24 am

  29. I have a 8500-iv hydro flame seies furnace in my 2003 Toy hauler.I have trouble shot to the best of my knowledge,the blower works,electrode works,but no power from ignition board to valve.also after electrode stops trying, red light on ignition board comes on.Any help would be appreciated.

    Comment by John — January 8, 2008 @ 6:38 pm

  30. Sounds like your board may have died – common problem, not too hard to fix. Go here and search your model number for T-shooting and repair help.

    Cheers (-:

    Comment by Roadless Warrior — January 9, 2008 @ 3:05 pm

  31. i have a suburban model NT-34L furnace. initial problem was a popping sound each time the burner lit. As i sleep with my head over the furnace, this got to be old in a hurry. I initially replaced the gasket around the burner access thinking that an air leak might cause the popping. still popped. I pulled the furnace, cleaned the blowers (intake and exhaust), removed the mud dauber nests, removed the burner and cleaned it as it 4 slots blocked with rust. reassembled furnace, reinstalled and guess what- furnace still pops upon ignition. It also will pop intermittantly if i let the furnace run. Gas flame is blue, some orange/yellow above the burner, flame kind of ripples right on the cast iron burner. no separation between flame and burner. Please advise and thank you.

    Comment by benjamin gee — January 17, 2008 @ 1:22 pm

  32. Sounds like we may all have a similar problem. I have a Suburban N-30M furnace with the same problem as mentioned above. Solenoid energizes but propane is not flowing. I replaced the solenoid valve.. still not working. Tested ewverything on the bench and found that the solenoid although clicking when powered, is not allowing flow when energized under pressure. If solenoid is energized and then the propane is thurned on, I get flow. Confused as to why this is happening. I even tried botha 20psi and 10psi propane regulator. Any suggestions would be appreciated.

    Comment by Rich A — February 16, 2008 @ 2:16 pm

  33. I found the answer to the post I made previously. The unit had been dropped off at my house by a friend who couldn’t fix it. I replaced the transformer and then ran into this “propane flow problem”. It seams he connected a supply line/regulator he had laying around to test the unit. This regulator was for 20 psi. Some research showed that the solenoid is only rated for 1.5 PSI. The hard piped line in the camper is regulated at this lower pressure and everything now works fine.

    Comment by Rich A — February 16, 2008 @ 3:54 pm

  34. Chris,
    My furnace blower fan just stopped working today. I tried/tested the furnace a couple more times with the thermostat igniting the furnacw with natural gas burning fine—just no blower fan. is the problem most likely a fan motor gone out or could it be something else.

    Comment by Jack — February 27, 2008 @ 4:46 pm

  35. Jack,
    Is this furnace an RV furnace? The only reason I ask is that in new RV furnaces, the burner cannot ignite until the blower is running.
    If it’s a house type furnace- I’m not that familiar with them, but usually the blower is controlled by a fan switch, which turns the blower on when the heat chamber reaches a set temperature.
    If it’s an RV furnace, I would suspect the fan relay.

    Comment by Chris — February 27, 2008 @ 7:54 pm

  36. I finally got the step working after another cleaning of the
    large 4 way plug and the door switch. It seems to stay out now.
    Thanks for the input.

    Comment by Bobby Simpson — March 4, 2008 @ 11:00 am

  37. I have a rudd furnece and it will be runing then it seems like a air pocket in the gass line and then theres 3 or 4 sucksons then the furnece shuts off then you here clicks then it starts back up right away and will stay runing and it will do this every now and then can you please help me thanks mike

    Comment by mike — March 4, 2008 @ 10:46 pm

  38. Hello:
    I have a suburban SF-20F and nothing happens. No blower no clicking nothing and its just past the warantee. I checked that it is getting power and the power is there. The thermostat is putting out voltage when I switch it to the heat setting. I was going to bypass the control module and put the hot wire right to the blower but I dont want to try things without some advice. Thanks for any help!!!

    Comment by Steve Rightnar — March 16, 2008 @ 9:28 pm

  39. I have a Suburban floor furnace in our 1992 Sandpiper. It has electronic ignition. When I turn the thermostat on the fan comes on and only blows cold air. I have been told this might be the thermostat but I do not know how to test it. Can anyone help. Thanks

    Comment by Steve P. — April 3, 2008 @ 12:14 am

  40. I wish that I would have found these posts before I tryed to fix my Suburban SF-30F furnace. The theromstat would start the fan, but there was no burner ignition. I removed the furnace. I took the burner apart and cleaned out the sand. I re-set the ignitor gap to 1/8 inch per the manual. After trying many different things, I jumpered the two blue thermostat wires instead of hooking up the thermostat. Then the furnace would start and light every time! Maybe a bad thermostat? I hooked up the thermostat again and found that the voltage to the limit switch was 7 to 8 VDC even when my converter was putting out 13.6 VDC, which is normal. I found a loose rivet in the Suburban thermostat, which I soldered (this can melt the plastic).
    This fixed the problem, but I still couldn’t explain why the thermostat was only getting 11 VDC when the furnace was running (10 VDC at the limit switch. I found a two volt drop on the positive power wire to the furnace, but only 0.25 volt drop on the ground return wire. I replace the power two wires with about 10 feet of # 14 wire so the furnace now runs at full voltage.

    Comment by Dale Randall — April 3, 2008 @ 5:38 pm

  41. In my ’04 Arctic Fox 24-5N, there resides a Suburban Furnace. It heats the
    5th very well and will be 5 years old in July.

    Since this is my first experience out of a tent or house, I thought my
    furnace was working properly all along, till late last year. That is when
    the steps in the furnace’s processes changed and made me think it may have
    been busted from the get-go.

    With the thermostat set at a temp higher than the room temp, I switch the
    thermostat from ‘off’ to ‘heat’. Here are the steps the furnace took the
    first 4 1/2 years;

    1. Instantly, the blower motor comes on. You can feel the air blow out the
    heater outlets in the floor.
    2. It heats the trailer very well and when it reaches the thermostat temp,
    the gas turns off and the blower continues to run.
    3. The blower runs for about 2 min. (I understand this to be the ‘cooling
    down’ time so the furnace doesn’t stop hot) At the end of this 2 min, the
    blower power goes off and the blower begins to wind down.
    4. Before the blower stops, it kicks back on and runs for another 2 min, at
    the end of which, it powers down.
    5. Before the blower stops, it kicks back on AGAIN and runs for another 2
    min at the end of which, it powers down and stops.
    6. The heater is off, waiting for the thermostat to tell it to turn on

    What changed to make me think this wasn’t normal?

    Sometimes, the heater will skip steps 4 and 5, or will repeat step 4 several
    times. The heater will cycle at least once, mostly 3 times, but up to 7
    times (that I know of). The air is blowing room temperature after the 1st or
    2nd cycle.


    Comment by FMB — April 4, 2008 @ 11:54 pm

  42. Hi FMB-
    I would guess that the furnace has been cycling on the limit switch- the thermostat is still calling for heat, but the furnace is getting to hot, shutting off and then cooling down and reigniting.
    This is usually caused by not enough ductwork or a disconnected duct pulling hot air back in to the intake.
    Given that yours has changed, I would guess that it was not enough ducts, and one may have split open- or you had a register that was closed that is now open.

    Sorry about that- I went and reread your post- it does sound like the relay- I’m assuming that you don’t have one of the newer models with the fan relay on the circuit board.

    Steve P- if you have a heat only thermostat , which only works the furnace, you can just take the wires off the thermostat and hook them together- the thermostat is simply an on/off switch.


    Comment by Chris — April 5, 2008 @ 8:08 am

  43. Chris, thanks for the reply. It is a SF30F and I don’t see a relay in the Installation instruction manual diagrams so I’m thinking it might be integral to the circuit board. I will have to pull the furnace out to determin that.

    Oh, wow. Am I glad you only struck through and didn’t delete your first comments. I always thought the bathroom floor vent didn’t blow much and the bedroom vent blew less (barely felt air move). I took the cover off to measure voltage on either side of the Hot limit switch and it dawned on me the amount of air blowing with the front cover off was enormous. With the cover off heater on, the blower sends copious amounts of heated air into the room through where the cover and cabinet intake vent would have been. When it came time to turn off, it went through a ~2 min cycle and turned off. I repeated this several times. With the covers on, it cycled 3-5 times. Hmmmm…. plugged vent tubing somewhere I’m guessing now, cause when I remove the vents out of the system, the heater works fine. Back to looking at vent tubing tomorrow. Thanks.

    Comment by FMB — April 10, 2008 @ 12:29 am

  44. I have a suburban furnace in a ’87 Winnebago.
    It worked fine until the day I needed it and then
    nothing. Any suggestions where to look first?

    Comment by Mike — April 23, 2008 @ 10:47 am

  45. I need some help! I have an Atwood Mobile Products Furnace in an 04 Bayhauler Trailer. (Mod # 8520-IV-DCLP) The wall Thermostat control is a Duo-Therm by Dometic. The furnace kicks on, ignites and blows hot air, unfortunately it si for a very short peroid of time. The heater will blow for a few minutes and shut off. The camper never gets warm. The heater has worked fine and now all of the sudden isn’t working right. He have taken the inside and outside cover off and blown air around to see if it could be dirty. Any suggestions?
    Thanks- if you can help it would be great it sure is cold in Wyoming!

    Comment by Jami — May 7, 2008 @ 10:42 pm

  46. I have 86 winnie motorhome with Atwood 7912 Hydro Flame,blower(fan)runs continuously when thermostat is turn, on but no ignition(flame),gas is on,would you give me a step by step run down so I can find and correct the problem? Thanks Rod.

    Comment by Rod Wesling — May 9, 2008 @ 2:58 pm

  47. Chris: Have a Suburban SF-35F furnace in an 05 Hornet Retreat. Has worked fine for the last 3 years until last weekend. Turned furnace to Heat and instead of the blower coming on and running for 30 seconds to 1 minute before igniting all we got was a buzzing noise coming from the furnace. Turned furnace off and buzzing noise remained until approximately 1-2 minutes before buzzing noise turned off…almost like a blower cycle time. Waited about 30 minutes, turned back on, same buzzing noise occurred. Pulled furnace out, and with switch in heat mode buzzing noise occurred and noticed blower fan moving very slowly. Tried it the next weekend to see if there was any difference, furnace did nothing, no buzzing, no blower, nothing. Any ideas?

    Comment by Doug H — May 20, 2008 @ 8:32 pm

  48. Hi Doug,
    It sounds like either the blower motor or the fan relay. I would hook 12 volt power directly to the blower motor to see if it will run OK (make sure the blower will turn freely, as well).
    If the furnace has the outside door, you should be able to do this without pulling the furnace out (IIRC).

    Comment by Chris — May 21, 2008 @ 2:02 pm

  49. Follow-up: Is the relay inside the furnace by the blower motor? No access door from the outside. Will there be 2 wires on the blower motor that I can hook 12v to, and is the white wire the ground on the furnace also?

    Comment by Doug H — May 21, 2008 @ 5:40 pm

  50. i have a wall furnace(no idea what the make is) and it is controlled by a wall thermostat. it started to make a popping sound and than a ball of fire would come out from the grill. turned it off and cleaned it up, called the gas co and they said to let the dust burn. turned it on after it had burned clean and it popped and fire came through again. we have been using it for the past 7 years and never had this occur before. any idea what it could be? thanks

    Comment by nicole — May 23, 2008 @ 10:10 pm

  51. Chris,

    I have a suburban furnace in my 01 Sierra. I have had an ongoing issue with the furnace that is frustrating me big time.

    With fully charged batteries my furnace will run 2/3 through the night before it stops igniting and the fan runs cold. Last year my converter went on the fritz and I figured it wasn’t charging the batteries good enough. This year I installed a PD power distro center with the charge wizard. I still get the same result from my furnace. If I plug my truck into the trailer the furnace will run all night but if it runs off my batteries alone it will stop 2/3 through the night. I have two deep cycle batteries that load test really well and through all this the lights in my trailer never go dim so batteries are not on my list.

    What is going on??

    I replaced the blower motor

    Comment by Doug S. — June 1, 2008 @ 10:12 pm

  52. Continued:

    I replaced the motor in my furnace, it was dirty and the bearings were rough. I figured this was my issue but it is not.

    Comment by Doug S. — June 1, 2008 @ 10:15 pm

  53. Hi Doug,
    I would bet that there is a voltage drop somewhere in the system- probably several, so even when the batteries are still up, the voltage to the circuit board gets low enough that it will not operate correctly.
    *If* the wall thermostat only works the furnace (and not the rooftop air conditioner), I would start there, but I’ve seen a lot of limit switches (which you access by removing the inside cover) with enough oxidation to severly drop the voltage- as well as the sail switch.

    Comment by Chris — June 2, 2008 @ 8:33 am

  54. My thermostat does control the rooftop A/C and the furnace. So I start by inspecting the limit switch(inside the furnace) and then the sail switch. What would the normal voltage drop across these components be?

    Is it safe to say seeing how the system works with the truck hooked up that the circuit board is OK?

    Comment by Doug S. — June 2, 2008 @ 8:54 pm

  55. My thermostat does control the rooftop A/C as well. I guess I will test the sail switch and the limit switch for voltage drops, what would you say is maximum acceptable across both these components?

    Is it safe to say my circuit board is operational with no issues or may I have an issue there?

    Comment by Doug S. — June 2, 2008 @ 8:58 pm

  56. i have a lennox system that the blower motor is staying on i chesck the limit swiths for conunity they r all fine i think it is the circuit board what do u think

    Comment by Anonymous — July 24, 2008 @ 12:35 pm

  57. i have an bryant gas furnace it was working fine on a summer eve.i had the a.c. on with the thermostat set on auto. I switched it to off,and also switched it to fan but the fan would not work. I tride a.c. with fan an d with auto. i also tride heat with fan and with auto. a.c unit out side turned on but no forced air.furnace turnd on but no forced air wat is the problem.

    Comment by kathie cooper — July 31, 2008 @ 7:03 pm

  58. Having problem with my Duo therm dometic Unit The ac will not cut off by itself when it reaches a certain degree you have to cut it off by the hi lo switch. It will not cut off with the Heat off Cool switch. I have replaced the thermostat, control board, and a compaster on top. Have checked wires need help I don’t know what else to check. please email me. Thanks

    Comment by Christine — August 20, 2008 @ 1:59 pm

  59. Hi Christine,
    It sounds like you have replaced everything I would check, but it is very possible that you got a bad (or wrong) thermostat. Dometic has many different thermostat/control box versions.
    Can you give any more information, like a part number for the circuit board or thermostat you installed?

    Comment by Chris — August 20, 2008 @ 5:10 pm

  60. I’m at work right now but I get off at 8 tonight I took the old one with me and got the same kind . Thank you for writting me back. I can;t thank you enough. I will write you back as soon as I get home Also it is doing the same things the other thermostat was doing. How it has been working On the thermostat there is heat off cool hi lo on auto. It use to cut off when it got a certain temp like if it is set on 70 it would cut off but know it will not. the fan goes from high to low fan and the only way you can cut it off is by switching it to lo with the hi lo switch. It will not cut off with the heat and cool switch when you cut it to off it cuts the fan on low. It was working fine till one night I was alseep and heard a pop and got up and heard the fan on low and every since then it hasen’t worked right. Thank you for your help.

    Comment by Christine — August 20, 2008 @ 5:37 pm

  61. Here aresome numbers I had wrotten down 3104757.004 control board 3104998 board and thermostat Relay kit serial #E6147786 for use with 579, 590, 595, 600 series Model 57915.421 Duo Therm Model 57915.421 product 991731645 Serial 61616390 Hopefully these will help.

    Comment by Christine — August 20, 2008 @ 6:11 pm

  62. Many apologies- I’m just not going to have time to research this right now, either here or on my RV.Net blog,as my shop and house are under water from TS Fay (and I only have about 1 hour of power per 6).
    Arghh…. about 15-20 inches of rain in the past 8 hours, with more to come :(.

    Comment by Chris — August 21, 2008 @ 5:11 pm

  63. sorry to hear that hope things get better. I will keep you in my prayers.

    Comment by Christine — August 22, 2008 @ 1:03 pm

  64. Hello Chris –
    First: Hope your home is ok after the flooding!
    Second: Thanks for a great resource & the personal responses for all here.

    Here’s hoping I can contribute something for those of us with older RV’s.

    Hunter 40020A mechanical thermostat sells for $10.20 at Lowes & is a generic replacement for the HEAT ONLY systems like my old camper’s Duo-Therm 65900 heat only furnace.

    Manuals for many furnaces & RV appliances can be found at

    Comment by Dwayne — September 21, 2008 @ 7:03 pm

  65. Manual link didn’t show up so here it is again:


    Comment by Dwayne — September 21, 2008 @ 7:05 pm

  66. I have a furnace not sure of the brand but sometimes it won`t ignite or it will after trying many times do you know what it could be?

    Comment by cameron — September 21, 2008 @ 11:52 pm

  67. by the way its a rv furnace in a 1982 23ft prowler

    Comment by cameron — September 21, 2008 @ 11:53 pm

  68. RV furnace will run 1 good cycle. On the second cycle,the blower comes on but no heat just cold air out the ducts. Need help please

    Comment by Tom — September 23, 2008 @ 6:30 am

  69. i live in a 1973 double wide mobile home. it has a coleman cool and heat furnace we replaced the blower moter, everything seams to work good now but the the transformer makes a humming noise all the time. my question is, is it normal for the humming or is the transformer no good, etc.

    Comment by larry — September 30, 2008 @ 2:46 am

  70. Hey Chris,
    I have a Rockwood pop-up with a Suburban DD-17DSI, I need to replace the thermostat but don’t know what to set the anticipator to. What does the anticipator do? If set wrong what could happen?

    Comment by Scott — October 12, 2008 @ 10:04 pm

  71. Hi Scott,
    The anticipator actually provides a very small amount of heat directly to the thermostat- so that the furnace will shut down just a bit before the set temperature is reached (because the furnace runs for a while blowing off residual heat) so that it will not get too hot.

    That said- the anticipator should be set at .7 for Suburban furnaces (1.0 for Atwood/Hydroflame)- a common mistake is to set it too far down (to .2 or .3) which will burn it out from too much heat.

    Comment by Chris — October 13, 2008 @ 5:00 pm

  72. I have a suburban furnace in my travel trailer and when i turn it on, after about 20 seconds the fan turns on an blows cols air and nothing els happens, but it is getting fuel though.

    Comment by travis j. — October 22, 2008 @ 9:20 pm

  73. I have a lennox propane furnace, it will light for a few seconds, then go out, re ignite, burn for a few seconds and go out….. have replaced regulator at tank did not fix, replaced line with new one, did not fix, what is left? Someone told me it sounded like water in propane tank. What does everyone think problem could be?


    Comment by Tommy — November 7, 2008 @ 4:14 pm

  74. Hi Tommy,
    I’m afraid I don’t have any knowledge of home style furnaces, but it sounds like one of two problems- either fuel (which you have dealt with partially), or the flame sensing not working.
    Home style furnaces use a lot of different methods to sense the flame, but I just don’t know about them.

    Comment by Chris — November 9, 2008 @ 6:15 pm

  75. Hi, I have a suburban furnace in my camper. when i turn it on it runs great for a while then the blower starts turning off and on at 2-5 second intervals. Do u have any idea what could be wrong? its getting cold =(

    Comment by Brenda Brooks — November 13, 2008 @ 9:41 pm

  76. I have a Suburban furnace in my RV. It fires and runs fine until it hits the set temperature. It then will not relight. The blower goes, and it sparks, but no gas. Anyone seen this before?

    Comment by Flip — November 14, 2008 @ 7:04 pm


    Comment by Anonymous — November 15, 2008 @ 8:37 am

  78. I have a similar problem Flip. I also have a Suburban furnace in my 89 travelmaster that does the same thing. Usually only in the middle of the night when everyone is asleep. Lost of good info in this thread though. I’m going to go out and start checking voltages.

    Comment by Chris M — November 22, 2008 @ 11:36 pm

  79. I have a 2006 cougar with a subarn furnace want come on with remote or by pushing heat butt no nothing what do i do

    Comment by Hammer — November 26, 2008 @ 7:23 pm

  80. i have coleman furnace ,when i light the pilot,it lights okay,but when i let up
    the switch to turn it on the pilot goes out.. i have got it started a couple of times
    the furnace has lit ,but after it cycled the pilot was off again

    Comment by robert lequier — November 27, 2008 @ 11:07 am

  81. sounds like the thermocoupler

    Comment by ty — December 2, 2008 @ 10:02 pm

  82. i have a suburban sf35 in a 92 bounder. turn it on ,blower starts up,you can hear the igniter clicking………..no ignition. the clicker comes on several times. no ignition. plenty of propane in the system. took apart unit ,checked the orafice.looked good cleaned it anyway,replaced,no change…..-any ideas???????????????????

    Comment by Ty — December 2, 2008 @ 10:14 pm


    Comment by Anonymous — December 3, 2008 @ 2:09 am

  84. OH! ALAN

    Comment by Anonymous — December 3, 2008 @ 2:12 am

  85. Sometimes soot can get into pipes and cause the furnace to go off and on without reaching the right temperture.

    Comment by Alan — December 3, 2008 @ 2:28 am

  86. Alan… I have duotherm ac with surban furnace. New thermostat… now the furnace won’t shut off until I disconnect all power.
    I disconected the red wire at the thermostat but the furnace
    just keeps on going.
    I doublechecked the wiring at the thermostat and it’s correct to mfg spec.
    Any ideas?
    Thanks, Don

    Comment by Don Mckernandoss — December 12, 2008 @ 12:36 pm

  87. I have a suburban sf35f, year 2005
    weird findings
    will not fire at 13.6 volts
    put a batt charger on at 12 v and it fires, drops to 10.8 v and runs fine
    fires every time

    Comment by Gordon — December 13, 2008 @ 12:03 pm

  88. I have a 1977 Traveleze Trailer. It has a Duo Therm Furnace. The pilot lights, But when we turn on the blower the burners turns on, then a minute later the burners shut off and so does the pilot. What could be the problem

    Comment by Anonymous — December 13, 2008 @ 9:40 pm

  89. Hi Don,
    I’m assuming you have a DuoTherm Analog wall thermostat- with a slider to set the temperature. On that setup, the furnace is actually controlled by the circuit board in the ceiling assembly, and is hooked to the blue wires with a white stripe. At the thermostat, the white wire is the furnace lead.

    Comment by Chris — December 14, 2008 @ 8:30 am

  90. Hi Gordon- that is odd. I would be tempted to look at the grounding (I always look at the grounding!), but it could just be a bad circuit board.

    Comment by Chris — December 14, 2008 @ 8:32 am

  91. Most of the time that’s a cleaning issue- the pilot is not burning correctly, and when the blower comes on, it pulls the pilot flame away from the thermocouple, so it then shuts down.
    Because of the age of that furnace, it really needs to be pulled, inspected and cleaned to make sure the combustion chamber is solid, and all gaskets are good.

    Comment by Chris — December 14, 2008 @ 8:34 am

  92. My friend called me and asked if I could help out with this problem. The only problem was is that I dont know how furnaces really work. He said that he can turn the heat on but it just blows air out not heat. What would be the first thing to check out frist? The theromstat,pressure switch or would there be another route you would take?

    Comment by Sammy Andrews — December 14, 2008 @ 12:08 pm

  93. my furnance just started acting up. theres a red light that flashes six times which tells me that the pressure switch has shut down. also ever since i ahve removed the face panel from the furnace it run great but when i replace the face panel. the furnance wont run properly…..what is going on?????

    Comment by david — December 14, 2008 @ 3:36 pm

  94. I think its a duncan it had a ignition switch that said off and on. down where the burners where it was not getting anything. I took pictures. I also changed out the thermostat and it still did the same thing. i turned it on and the fan and blower came on but no heat. Please help.

    Comment by Sammy Andrews — December 14, 2008 @ 9:48 pm

  95. We have a Suburban SF 25F, last night it blew cold air long enough to get to 45 in the camper and wake me up – it was 8 outside. I turned off the furnace for a while, then turned it back on, it blew warm air for about 15 minutes, then the air turned cold again. Any help or suggestions would be great…thanks!

    Comment by Cold in Nevada — December 17, 2008 @ 9:48 am

  96. We live in a 1979 35ft Komfort fifth wheel and had a Suburban NT30SP, which we had to replace exactly one year ago with a supposedly NEW one (from an RV supplier), same model. We have already replaced the igniter a month ago, and now the furnace is doing the same thing again. We bought an extra igniter last month, but that isn’t working. Still have the same problem, fan but no flame. Are we going to have to go throught this every winter? We lived in the RV for 10 years before we had to replace the heater. And with the new heater, seems as though we may have a lemon. Any recourse with that?

    Comment by Patricia — December 18, 2008 @ 2:10 pm

  97. Where in Nevada? We are in Dayton, NV Having trouble with our heater, too, and we installed it NEW last Dec., fan but no flame. Already replaced the igniter, twice!
    But this time it isn’t fixing the problem. Further troubleshooting needed. Temps near 0 now. Sure can’t afford to buy another new heater @ $700.00 Any suggestions out there????????

    Comment by Pat in Nevada — December 18, 2008 @ 2:19 pm

  98. Hi David,
    A couple of things come to mind- there is an air prover (a.k.a. sail switch) right inside the outer plastic blower housing. It sounds like this is either bad, or the return air is blocked somewhat, or the voltage is low and the motor isn’t turning quite fast enough.

    Comment by Chris — December 18, 2008 @ 2:29 pm

  99. On that model I have found the limit switch is the most failure prone part- you can easily get to it from inside the rig- there will be n access panel (the whole inside panel) that is held on by a couple of screws, and the limit switch is right behind it- it’s a small oval switch with two wires leading to it.
    Often simply disconnecting and reconnecting the wires will fix it for a while.

    Comment by Chris — December 18, 2008 @ 2:32 pm

  100. Hi Patricia,
    That really isn’t normal- really the only design problem I see with the NT series is that the circuit board is too close to the combustion chamber- Dinosaur makes a board extender which will move the circuit board outside the case, which both keeps it cooler and makes it much easier to troubleshoot.
    That said- I would closely look at the installation- especially supply and return air flow, as well as trying to bypass the thermostat to test.

    Comment by Chris — December 18, 2008 @ 2:37 pm

  101. Already bypassed thermostat. Heater was working fine this morning at 6:30 when we turned thermostat up (we turn it lower at night). But by 7:00 it was no longer igniting.

    Comment by Pat ricia — December 18, 2008 @ 3:22 pm

  102. I have a Suburban NT30sp when I turn it on and adjust the thermostat to a high temp, the blower comes on , but the burners do not light and I can’t hear the igniter sparking, want could be the problem

    Comment by Pat — December 25, 2008 @ 10:45 pm

  103. My old duo-therm just stopped lighting up, the blower comes on but no heat. I replaced the controller board with a 50 plus board. Now the blower comes “ON”, I hear the igniter and smell the gas coming out the exhaust, but it just won’t light up. I have tried adjusting the air shutter, but it just won’t light. Any ideas?

    Comment by george — December 26, 2008 @ 8:08 pm

  104. 1st, thank you for what you are doing here!

    I have an 06 Laredo with a Suburban NT-30SP heater and a Colman Mach thermastat (Air & heat)

    I have had the unit in shop several times for this problem, but they could not resolve.

    Problem: Heater comes on, heats, cools down, turns off and then immeditaly turns back on. It will stay on for several minutes, (No heat) turn off, and again immeditaly turn back on. This cycle continues untill I turn off at thermastat.

    I need to use this unit this week for additional rooms as family is staying for wedding.

    Thanks again for this,
    Bill Z

    Comment by Bill Zimmerman — December 28, 2008 @ 1:56 pm

  105. Chris,

    I have a 1976 Winnebago Brave. My furnace won’t stay lit, but when I relight the pilot, it stays on until I turn the furnace on, then the pilot goes out. I have changed the tanks and regulator and hoses, and now the pilot won’t stay lit. I bought a thermocouple, but don’t know how to change it. Any tips, and do you think that is the problem?



    Comment by Bill — December 28, 2008 @ 6:04 pm

  106. I would like to know why my furnace blows cold air after running for a while, it doesnt do this all the time but every once in a while it starts to blow cold air and I have to turn it off and re-set it.

    Comment by shelia d. hobbs — January 7, 2009 @ 2:26 pm

  107. Why does my furnace click on for 3 seconds then clicks off, then back on again and stays on till it reaches temperture?

    Comment by Anonymous — January 8, 2009 @ 9:54 am

  108. Hey Chris, I have a Suburban nt30s in my RV. When I turn the thermostat on, the blower will come on and the electrode sparks but the pilot does not light. I repeated this about 10 times and still no pilot. Any Ideas?
    Thanks, Scott

    Comment by Scott Poynter — January 11, 2009 @ 5:15 pm

  109. Hi Scott,
    It sounds like it isn’t getting fuel (propane). The “quick and dirty” check for a sticking gas valve is to take the front off the furnace (so you can see when it’s trying to ignite), and when it fires the spark, give it a good sharp whack on the gas manifold- not too hard, but a sharp thwack.
    The bad part is that if it ignites, you will have to replace the gas valve, as while it may work for a while, the valve could be leaking (not real common), and it will likely fail again at the worst possible moment.

    Comment by Chris — January 11, 2009 @ 5:53 pm

  110. I have a heating wall furnace and it will not cut off. The fan runs and the heat runs. I have replaced the thermorestat and it still will not cut off when you turn down the temperture. I disconnected the power from the gas control and then the gas burner cut off and the fan ran till the temperture dropped like it should. Do you know what could be wrong. Can I fix it or should I call a repair man.

    Comment by John Beal — January 12, 2009 @ 2:39 pm

  111. I am having an odd issue I haven’t seen posted yet. I have a Suburban Nt series in my 33′ Komfort ducted unit. Last year I had the issue of the furnace not turning off when it reached temp. It only happened occasionally. This year it started right away so I replaced the Thermostat, that seemed to help for awhile and now it is doing it again. The furnace was replaced about 2 years ago, but the thermostat was the original so Replaced it with an identical new one. Thermostat is Duo-Therm and does control the Roof top AC. Any suggestions would be great!

    Comment by Jim — January 13, 2009 @ 11:17 am

  112. i have three circulators for three floors in my home. the basement works the second floor works however, the first floor dosen’t work. i replaced the circulator pump and noticed it dosen’t work is it possible there is a seperate relay for the first floor. how do i test this i have an electronic reader.

    Comment by bomani — January 17, 2009 @ 6:50 pm

  113. i have three seperate floor with 3 different circulators. one of them isn’t working how can i test this. by the way i replaced the circulator already because it wasnt working. does the relay seperate them and can i check them seperate

    Comment by bomani — January 17, 2009 @ 6:56 pm

  114. hi i am home owner and i have problem with my furnace ,if somebody can help me with this i will thank , well the problem is when i turn the thermostat to heat the condensing unit out side it come on and turn off and some time stay on so is blowing cool and warm air and the same time i dont know if the problem is the fan control board thanks u

    Comment by eddie — January 18, 2009 @ 12:56 am

  115. We recently moved our Shadow Cruiser 5th wheel and when we turned the heat on the fan made a horrible racket and the lights went dim and it blew the fuse. It has been doing this ever since. Is it the motor or something else?

    Comment by rebecca — January 19, 2009 @ 9:03 pm

  116. We have an Attitude Trailer with a Suburban SF 30 Furnace. The furnace will not stop blowing heat, even with the thermostat in the off position. We replaced the wall thermostat but it didn’t solve the problem.

    Comment by steve — January 22, 2009 @ 11:48 pm

  117. Hopefully this will prove helpfull for some of you above.
    I was repeatedly having a similar problem with my Hydroflame and by accident found that removing with a toothbrush, the dust bunnies and grime that seems to accumulate rather quickly on, in and around the circuit board, the blades of the “squirrell cage” fan and shroud (which also includes the sail switch, interior of furnace compartment and any air inlets to the furnace inside the RV, totaly fixed the problem and allowed me to gear up for the next thing to go awry in my aging RV. Sounds stupid, but apparently these things really need to breathe and grime build up on the fan blades seems to throw off the motors balance resulting in awful sounds while running, earlier demise of the motor and sub optimum performance.


    Comment by Eric — January 24, 2009 @ 4:11 pm

  118. I just had some dealings with a similar situation. Inside the motor housing is a magnet / coil assembly with brushes, like the inside of a power drill but bigger. Over time and especially in wet weather, dust from the rotation friction accumulates inside the motor housing and clogs up the motor. With a bit of patience and a little forethought, the motors’ housing can be removed and the interior cleaned with a dry toothbrush and the assembly put back together. The insides are magnetized and will offer some resistance but they will come apart.
    It is imperative that the motors cap NOT be removed from the coil shaft as the brushes are mounted to the underside of the cap and are tight to the shaft. if the cap and shaft part ways then good luck getting them back together without breaking the brushes. GOOD LUCK.

    Comment by Eric — January 25, 2009 @ 1:42 am


    Comment by Eric — January 25, 2009 @ 2:04 am

  120. I have a Hydro flame furnace and thermostat in my ’92 Dutchmen ct. We’ve had a number of problems with the furnace over the last four years, but partially with the help of your page, I’ve been able to always get it going again. But recently it pulled a mind scramble on me and just quit working at all. I mean completely lifeless. No noises or actions of any kind. So far I’ve cleaned thoroughly the entire unit and it’s components, bought a new motor (being careful to draw a color coded wiring diagram before taking everything apart) but once back together there was still no life. I bought a new deep cycle battery and replaced the cable ends but still no sign of life. Next I cleaned and rebuilt the thermostat, replacing the sensor wire in the process and checking that the anticipator is set correctly but still no life I haven’t a clue how to use a multimeter or manometer even if I had one. I really need a good clue as to where to go from here. Tired of wearing coat and hat in the house.

    Comment by Eric — January 25, 2009 @ 3:11 am

  121. My furnace has a wild occasional problem. The ignighter comes on, then the three burners, and after about 3 seconds. the burners cut out and resets its self. It will do this about four times then completely turn off. After 10 minutes it will cycle normally for 2 times and then after those cycles it repeats its self with the burners cutting off. The gas valve is on ive checked the grounds and the flame sensor and flame rollout switch.

    Comment by Matt — January 28, 2009 @ 11:58 am

  122. I have a 07 KZ Montego Bay F/W. The air flow going into the bedroom is very low and I have to set the thermostat to approx. 78 deg for it to run long enough to heat the rig. When the furnace shuts down it comes right back on again sometimes in as little as 30 sec. I have plenty of air flow to the living area. The furnace is located in the basement area. What could cause low air flow to the bedroom and why does the furnace turn right back on after shutting down?


    Comment by Kathy — January 30, 2009 @ 12:19 pm

  123. I have a 2003 keystone tailgator 5 th wheel ,329t5. Furnace works good, so I think. I just got this camper and this is my first time using it. Furnace comes on and heats good, cycles, but the floor vent closest to the furnace is so hot that it will burn your feet. When I got home from a trip I noticed that the plastic lovers in that vent had gotten so hot that it warped the lovers out of shape. Any thought on this will be appreciated. thank you sid

    Comment by sidney mcwhorter — February 1, 2009 @ 10:44 pm

  124. Gas Furnace combustion blower continues to run for long period after thermostat has shut off burner. Runs 15-20 minutes before turning off. All else works OK.

    -Pete, in Tacoma WA

    Comment by Pete — February 9, 2009 @ 2:33 pm

  125. Hi Pete,
    That sounds like the fan relay- a time delay device.

    Comment by Chris — February 9, 2009 @ 6:30 pm

  126. @Jean, The emg stands for emergency heat which are heat strips built in to the air handler for extra heat. You might not have these strips and are just blowing the fan without any heat. A true heat pump doesn’t need propane but should heat with a reversing valve near the compressor. A tech needs to reconfigure your thermostat for what you have. If you have a true heat pump the supply air will be arouind 105-110 degree in heating mode, LP will be hotter,125ish.

    Comment by Mike — February 15, 2009 @ 2:13 pm

  127. hi chris ihave a sf30f that worked great until late fall it just wont spark i have removed the furnace and ohmed out the ignition wire and is good. blower kicks on correctly just no spark ………….my theory is the curcuit board is bad…..is there a way to test the board?? sail switch ok , and relay swich is good however i am trying to test w/o propane hooked up but im assuming that should not affect the ignition spark. obvisously no flame of course

    Comment by Ron — February 15, 2009 @ 8:46 pm

  128. furnace comes on, fan gets speed, element heat up; then no gas,element cools ; this repeats a few times, then shuts down. help me if you can.

    Comment by rwh — February 20, 2009 @ 3:17 pm

  129. Hi, Have a Suburban SF30F propane furnace which responds as such: Fan comes on, ignition,
    element heats up, flame goes out, ignition again, element heats up, flame goes out, ignition
    again, element heats up, flame goes out, element cools off, several minutes later the fan turns off.
    Problem remains even with thermostat jumpered, combustion chamber cleaned out, igniter
    aligned to burner. Do you have any suggestions ?

    Comment by Art Dill — February 21, 2009 @ 7:16 pm

  130. Hi Art,
    I would look at the limit switch, which seems to be the most failure prone part of that model, in my experience.

    Comment by Chris — February 22, 2009 @ 9:52 am

  131. IMy furnace was working but then about every 2 days or so the fan would kick on and then I wait to here the flames ignite and nothing happened. I wen into the basement and switched the furnace off and on and then the fan went on-the ignition senmsor got red and the gas fired up. I put in a new electric ignition sensor and still have problems-every once in a while the fan starts but the electirc ignition sensor.

    Comment by ron dernick — February 26, 2009 @ 3:45 pm

  132. Look at replacing the gas solenoid combination valve, I paid $119, Mine was getting current but not always clicking open as to be expected 15 seconds after fan starts and ignitor heated up.

    Comment by Jack — March 18, 2009 @ 1:40 pm

  133. Have an atwoood excalibur 8500-ll furnace. Just found out the burner assembly is totally bruned out. The electrode is ok. What effect does a burnt out burner assembly have on the operation of the furnace? Would it cause the furnace to light and run for a few seconds then shut down?

    Comment by FRED — March 19, 2009 @ 1:25 am

  134. if your batteries are not fully charged the ignitor will not work and you will need get lp to the furnace. try charging batteries or having them checked

    Comment by Anonymous — March 21, 2009 @ 11:03 pm

  135. I have a lennox gas furnace I replaced the thermocouple this fall It was fine untill 2 months ago the pilot light keeps going out whats wrong?

    Comment by robert — March 28, 2009 @ 5:26 pm

  136. I have a Suburban SF-35F furnace with a Dometic analog t-stat, heat/cool only no heat pump or strip. The furnace has a recently installed Dinasaur board. It works fine by connecting the two blue stat wires but when I pulled the furnace I didn’t label the blue wires coming from the wall. How do I know which stat wire goes where? One of the stat wires coming from the furnace is always hot as the other is not. Neither one of the blue of the blue wires from the wall is hot with the stat in any position. Any info is appreciated. Thank You

    Comment by Dan — March 30, 2009 @ 11:49 pm

  137. I have a Suburban Furnace model # NT24M. I am looking for a thermostat relay. Do you know where I could fnd one?

    Comment by Paul LeDoux — April 1, 2009 @ 10:27 pm

  138. Christine…Do you have your old part 3104757.004 Control Board. I cannot find one anywhere. Did you ever determine if it was defective, if not, would you be interested in selling it to me?

    Comment by Chad — April 20, 2009 @ 11:33 pm

  139. I have a 2005 vortex toy box 27 foot the furnance wont light the blower comes on, and runs for a few minutes but the heater wont light , than the blower will shut back off. Any suggestions

    Comment by michael — April 28, 2009 @ 10:23 pm

  140. Hi Chris, enjoy your website. I have a 94 wilderness with a Hydroflame 8525 ll. The blower kicks on and the flame will ignite for 4-6 seconds then lock out. I’ve pulled the unit out and have hooked it to 12 volts – propane. I’ve also pulled the burner unit out to physically see what it is doing. I have been performing T/S on the bench. However I haven’t been able to find a service manual that will give me specific info & specs. I have confirmed the 12v back to the circuit board thru the sail & limit switches. I have also tryed preheating the thermocouple. No change. Next I have been measuring the volt change of the thermocouple back at the circuit board. I can see voltage change during the 4 seconds the burner is lit. I am wondering how much voltage the circuit board wants to see. note: the thermocouple doesn’t look damaged in any way. Help?!

    Comment by MASTC — May 3, 2009 @ 11:54 am

  141. Hi Chris,
    I have a Suburban gas furnace and it will not run. I checked the t stat and in furnace mode I was reading from ground to furnace 0 vdc. I switch to off anf from ground to furnace I read 13 vdc. shouldn’t it be the other way. Also when in furnace mode and I turn the fan from auto to fan only the A/C fan comes on. Any sugestions. Thanks

    Comment by Bill — May 7, 2009 @ 10:11 pm

  142. Chris,
    I have the same problems with my 07 Sudurban 35 as your other troubled writers. Blower starts, spark-board attempts all three times, you can smell gas outside – but no firing! Replaced the regulator 6 months ago, and then it worked for a few months – – can’t believe that they fail that often?! If this many people have this many problems, is there some other manufacturer that makes a reliable replacement unit with easy access for annual cleaning? I started full time RVing 3 years ago – but these furnace problems are a real pain and the worst headache of all maintenence!! Design a furnace that lasts, and become a millionaire Chris!! Thanks, Dan

    Comment by Dan Crocker — May 9, 2009 @ 2:15 pm

  143. I have an Amana Gas-fired warm air furnace and / Amana ac remote condesing unit. 3 years old, last fall I had a board replaced in the furnace it would not work. Now today the fan won’t start , AC won’t work, furnace won’t work. Making me crazy and broke I’m a senior on fixed income. Please any suggestions

    Comment by Jack Biggs — May 23, 2009 @ 8:27 pm

  144. Chris
    I have a coleman furnace (dont remember the model) in a mid 70’s road runner. it is set up for 110v or 12 v . but on 12 v it doesnt seem to kick over from pilot to burn. It has the glow coil to light the pilot and on 110 its fine but on 12 v it just wont quite do it. but yet the 12v batt will run the fan just fine . if i take a set of jumper cables and hook up to an extra batt when the burner clicks( trying to light) i can get it to work. any help? thanks…

    Comment by Robert — May 27, 2009 @ 4:46 pm

  145. Your suggestion sounds great; however, I have a hydro flame furnace (8516), and the thermostat (Robertshaw) burns out, making it a little difficult to measure the amps across the thermostat. I presume something is drawing to much current, and I would like to measure it. It worked fine the first night on our last trip, but the next night there were no heat. Back home I replaced the thermostat – a flash – and it was burned out to. I am connecting the the hot wire to the pole marked red common. Any suggestions or help please! Thanks.

    Comment by kristian — May 28, 2009 @ 7:24 pm

  146. I recently installed a carrier condensing unit line set and A-coil for a friend. I wired everything back the way I disassembled it. The cooling unit ran fine all night except the electronic controlled t-stat failed to control to set point. The person said it coled the house down fine but in the middle of the night they got too cold and when they looked at the t-stat they realized the room temp was lower that the set point. They manually shut the cooling off and when they got up the next day the house was hot and they went to turn on the cooling on the t-stat nothing happened. I thought it was a t-stat issue so I replaced it and still no cooling. I can manually force the contactors on condensing unit with a screw driver on but not automatically.The same can be done with the fan on furnace. Can you tell me what the issue can be?? Do I have a bad circuit board due to something the person did when they manually shut the cooling down the first time?


    Comment by Brian — June 21, 2009 @ 10:12 am

  147. Hi, I have an Atwood Hydroflame 7920-II model furnace in my coleman pop up camper. When I turn the furnace on at the thermostat, the fan kicks on and runs, but it does not blow hot air. If I leave it on it just keeps running and doesn’t shut off, any body have suggestions on basic issues that I can check out to try and fix this?

    Comment by Kurt — June 23, 2009 @ 1:21 pm

  148. have suburban furnace model# SF 30F with a valve shut off switch which i cannot locate,any ideas??

    Comment by ken — July 10, 2009 @ 8:50 am

  149. It should be attached to the blower cover, accessed from the outside- but.. if you don’t have an outside removable cover, you will have to pull the furnace to get to it.

    Comment by Chris — July 10, 2009 @ 12:39 pm

  150. I have a Suburban SF 30F furnace in my 2008 Tango and the furnace has ran almost every night since we bought the trailer. We live in Canada so it does cool of at night. My furance would kick in fine but it would not light. We can smell propane coming out the exhaust and we can hear the ignitor clicking. Once and a while we can fell a warm puff as it does light for a split second. The only way we got it to light was to tap off a third of the air intake then it ran fine. To me if looks like an air / fuel mixture problem. does anyone know if the air / fuel can be adjusted?

    Comment by csklatt — July 13, 2009 @ 9:12 am

  151. I have an older Coleman furnace in a 1978 motorhome. After winter vacuum of dust and rust from pilot, replaced thermocouple, etc runs like champ again. However, when the thermostat shuts off, the flame and fan all shutoff together. Is that OK, seem like hot shut down with no cool down would be bad for it. Any suggestions would be greatly appreciated.


    Comment by Morgan — July 14, 2009 @ 11:23 am

  152. It really isn’t adjustable, but from the symptoms I would bet you have either low LP pressure, or a partially clogged orifice.

    Comment by Chris — July 14, 2009 @ 12:10 pm

  153. There should be a thermal fan switch in the blower circuit which keeps the blower running for cool down.
    But… you do have to run it long enough to heat the switch up before it will engage.

    Comment by Chris — July 14, 2009 @ 12:11 pm

  154. Hello Chris: We have a 2000 Flagstaff tent trailer. We have had the trailer out several times this year and the furnace worked GREAT! On our last weekend out, we blew a circuit in the trailer, but were able to reset it, and we believe the furnace came on that night as expected.

    Last weekend though it was a bit chilly at night, so we turned on the thermostat, but the blower only blows out cold air now. We have checked all the fuses and circuit breakers in the panel and all looks good there.

    My husband has checked and the fridge and propane stove are working. He checked and the propane tank is full (in fact it was filled just before we went out last weekend)

    Is it enough information to suggest where we should start? Thermostat?

    Comment by Kathy Chapman — July 18, 2009 @ 7:12 pm

  155. it more than likely is not water in tank. its very difficult to get water to gas valve unless you have open line and it rains or someone puts it in there,then connect s tank. could be vent problem.

    Comment by garry — July 21, 2009 @ 6:19 pm

  156. thermocouple or clogged pilot orifice.

    Comment by garry — July 21, 2009 @ 6:26 pm

  157. in case of flame outage so gas would not escape into heat chamber

    Comment by garry — July 21, 2009 @ 6:27 pm

  158. the tank regulator should prevent pressure problems from the tank unless it has malfunctioned.

    Comment by garry — July 21, 2009 @ 8:10 pm

  159. We have a Suburban Furnace in a 1982 Starcraft. Model# GT-10DB. We light pilot, and when we turn the knob to ON the pilot goes outt. One day we were lucky enough to have it stay lit when turned to ON position….but no blower, or any fan noise. Any help appreciated, as husband and myself are fighting over it constantly!

    Comment by Ty — July 31, 2009 @ 10:21 pm

  160. Chris – this is a great website! I have a problem with my suburban furnace in that it keeps blowing the 15 amp fuse. When I turn the stat on nothing happens. I have been able to get the blower to come on by manually spinning it and turning on the stat and then it starts to function and even the works properly at that point, but after about five minutes it blows the fuse again. Do I have a bad blower or is the relay toast? Is there a way to clean the blower if that is the problem in that it is just dirty and won’t spin thus drawing too many amps and blowing the fuse. I did just replace the Tstat as the old one was not working at all. I did not look at the anticipator but will set to .7 on monday and try again. LMK if I need to try something else. Thanks!

    Comment by Dan Cohen — August 30, 2009 @ 11:09 am

  161. I have a suburban SF-30F and used it for the first time this season. The unit turns on and runs also shuts off at set point. The only thing that is bothering me is the popping sound coming from the exhaust port. I pulled the unit out and cleaned found nothing significant. The hot water heater works fine with nearly full propane tanks. Any thoughts? Thanks

    Comment by Tony Cobuccio — August 31, 2009 @ 11:31 am

  162. Hi all>> Ok, I have a 92 40′ fifthwheel Alfa to be exact. Had issues with original furnace so they put in new Suburban N40 I believe. It worked a few times then stopped. They came back. Took it out and to shop. Brought it back and it worked a couple times and went out. They took it back to shop again and brought it back and it worked about three times and quit. This has gone on for months and finally the company that was working on it gave up and said he does not know what to do. It will not do anything, no click or nothing. I even tried putting in new ignitor but nothing. I don’t know what to do now as they won’t even try to repair it anymore. It cost over a thousand dollars for the furnace and I don’t know how much for all the travelling and repairs but it was a lot.
    HELP PLEASE. Winter is coming and I live in it.

    Comment by Jean — September 4, 2009 @ 2:54 pm

  163. Thank you for what you do.

    Interesting info in this blog…I believe I have my issue isolated but would like to confirm. Hydroflame 8500 starts and heats correctly, but after flameout, the blower continues to run…..forever. The relay is hot to the touch while running and of course when I unplug the wire going to the blower, it stops. If I plug it back in immediately, it will resume running. If I wait 5 minutes or so and plug the wire back in, it stays off until the thermostat calls for heat again and the scenario replays itself. Any help is appreciated.

    Thank You,


    Comment by Daniel — September 6, 2009 @ 9:15 am

  164. Hi Daniel,
    I would say the fan relay is bad. While this isn’t terribly common, I have seen it before.

    Comment by Chris — September 6, 2009 @ 5:06 pm

  165. Glad I found this blog.

    My problem is unusual. My funace (suburban) goes on fine. Once it reaches the set temperature it also shuts down properly. But then when the ambient temperature goes down the furnace never goes back on. What I need to do at that point is bring the thermostat’s set temp down and then right back up and the cycle described starts ober and over.

    Please help me…. I was up all night playing with the thermostat… trying not to freeze !!!

    Comment by Pierre — September 7, 2009 @ 9:54 pm

  166. Chris- I have a 90 Hydro Flame 8500-11 that when I turn it on the blower works fine but it won’t ignite. If I turn the thermostat down and then back up the fan continues to blow and the burner ignites. The next time it kicks on the same thing happens. The blower will run for hours because it never ignites unless I manually play with the thermostat. I have also replaced the thermostat. Any ideas. All other gas appliances work fine. Thanks for your help.

    Comment by Beau — September 8, 2009 @ 4:05 pm

  167. Thank you Chris. As suspected the fan relay was bad. Replaced it at a cost of 36.00 and it now cycles the fan off after burner cooldown period. Problem solved.

    Comment by Daniel — September 11, 2009 @ 6:53 am

  168. I have a Rheem Corsaire gas furnace (cat 1 forced air) and when the furnace is off there is a continual buzzing sound. It sounds like a motor running but I can’t feel any vibrations or pinpoint the origin. Any suggestions? Thanks!

    Comment by ali — September 16, 2009 @ 10:51 am

  169. I have a 76 camper with a duo-therm. Every time I turn it on it keeps blowing out pilot

    Comment by jACK — September 19, 2009 @ 8:22 am

  170. Hello Chris,
    I have 2 Suburban Furnaces in my 85 Bounder. Sf=20 and sf-35 and neither will ignite now. I put the dinasour board from the sf-20 in the sf-35 and it ignited a few times then it quit igniting, . I’ve replace both limit switches and the sail switch in the 35, but no avail. I also replace the themostate for the sf-35. Is it possible that they are not getting enough voltage, or do they need grounding?? I also had the sf-35 serviced a couple of years ago, but I took the unit in not the RV. Please help, it looks like their is alot of people with this same ignition problem. Thanks. Wayne

    Comment by Wayne Diggins — September 21, 2009 @ 9:26 am

  171. Hello Chris;
    Last winter while at my hunting lease my Suburban NT30SP RV Furnace would work fine for several hours and then after it cut out after reaching the thermostat set temperature the blower would come on but the burner would not light until I got up and recycled the system using the thermostat…turned it off and after a few minutes turned it back on. Sometime it would go fine until morning and at other times it would repeat the fault. I have purchased a new temperature limit switch. Do you think that may be my problem? Thanks, Al Barrs [email protected]

    Comment by Al Barrs — September 25, 2009 @ 2:25 pm

  172. I have a 2003 Keystone (sprinter) 5th wheel. The furance works sometimes. You can feel cold air blowing and that it is try to click on. So we run it for awhile turning it off and on no hot air. Then I tried it again the next day and it worked. But 2 days later did not worked. I think this thing has a mind of it’s own. Do you think you can help me out. Please it is getting pretty cold at night up here in eastern washington state. Thanks Wendy

    Comment by Wendy — September 26, 2009 @ 10:37 am

  173. My trailer furnace flame is to yellow, I cleaned the burner but that didn’t help.


    Comment by Rob — October 2, 2009 @ 11:43 am

  174. Hi, I need help with our furnace! We just got a Keystone Outback travel trailer 26rs which has a remote for the ac/furnace. We bought 2 new marine batteries and had the generator on, tried the ac and it worked fine….changed the mode to furnace and increased the temperature and nothing. We tried everything and nothing is happening. Can you help?

    Comment by Tina — October 5, 2009 @ 10:45 am

  175. have a atwood furnace model 85-11, the blower comes on, but on heat. I’ve played with the thermastast, no heat what could be the problem

    Comment by leonard andrews — October 5, 2009 @ 2:36 pm

  176. i have a problem. I have a 1978 dodge commander with a duo therm 65920-041. The pilot light stays lit. Has been lit for the past 2 days. The problem im having is that when i turn the thermostat on (ive kept it on for 2 days also) the blower doesnt work at all. No noise no nothing. It has came on one day. I was cooking.. I heard it going and got all excited… Then the next day.. Nothing. Any ideas?

    Comment by jennifer — October 6, 2009 @ 3:53 pm

  177. Hello I have a Suburban SF-25F LP Gas Furnace. The unit works BUT when it is turned off I can smell a small amount of LP gas coming from the outside exhaust vent of the unit. So far from the internet I have learned that # 1 the valve could be bad or #2 the electronic module could be bad and be sending current to the valve allowing it to open. How do I do I figure out which one is bad?

    Comment by John in Miami Florida — October 7, 2009 @ 3:05 pm

  178. I have a very old International furnace, we recently just moved in and are trying to save on cost. We have comepletely cleaned the furnace and it is obvious that it hasn’t been maintained in years. The flames are very high and orange, and when we adjusted the regulator to where the flames are blue and 1” high the last burner goes out. Do we need to replace the gas regulator valve, or is there anything else you could suggest before we call a proffesional?

    Comment by Tabitha — October 14, 2009 @ 3:51 pm

  179. I just installed a replacement burner motor on my older forced air oil furnace. the system fired up perfectly after bleeding the line but quits firing after 10-15 min! The forced air fan kicks up when limiter triggers it, but burner shuts down when it reaches its 200 mark. Fan keeps going for another 10 min but burner never automatically fires up again, unless I manually reset the furnace relay botton.
    (NOTE: The red reset relay is cranky…I often have to push it repeatedly for it to engage & fire up.)
    A) Why is the burner reaching it’s limit so soon?
    B) Is the furnace reset relay defective? (preventing burner from refiring automatically? And since I may also have damaged the Fan/Limit switch by not holding down the disk while resetting;
    C) Could BOTH Fan/Limit switch & Reset Relay be causing the short firing time?
    ( I have not yet cleaned out the stacks)
    Thank you for any suggestions or clearing any missconceptions…


    Comment by Antones — October 16, 2009 @ 5:16 pm

  180. Well Wendy, you could always park that 5th wheel down here in FL .. it was 85 degrees here today and rarely goes into the 50’s in S. Florida – in the meantime, have ya fixed that pesky furnace of yours? LOL

    Comment by Dennis — October 17, 2009 @ 12:00 am

  181. We have a stationary RV. My wife and I were just up to close up for the season. I had just been up myself to the trailer about three weeks previous and torned the heater on, which seemed to work fine. Before I left I turned the thermostatat down all the way as usual before I left.
    When we arrived and opened the trailer the blower was on. I don’t know how long it had been on. I finally opened the circuit breaker panel and shut the circuit off. This circuit also handled the trailer ceiling lights and several outlets.
    I was going to turn the propane on and see if the heater would fire up but was reluctant too. It was extremely cold so we had to get a room at a local motel.
    The next morning we returned and when I turned on the circuit the blower fan went on again so I re-shut off the breaker.
    Later that day after installing anti-freeze in the water lines I had to open the circuit to turn on the water pump. This was the same circuit as the blower. When I re-set the circuit breaker this time the blower fan did not come on.
    My first thought is that it might be a faulty thermostat, which I plan to replace to see if that’s the problem.
    My questions are:
    1. Could a bad thermostat be a reason for the blower fan to just start on it’s own?
    2. I didn’t get the name of the furnace before we left (5 hours away). Can any thermostat be installed? The type I have has a lever on the botton but it does’nt seem to move so I never really touch this lever. The lever at the top sets / regulates the tempeerature and this is what I use to turn the heater on and off.

    Comment by ak — October 17, 2009 @ 9:13 pm

  182. We have a stationary RV. My wife and I were just up to close up for the season. I had just been up myself to the trailer about three weeks previous and turned the heater on, which seemed to work fine. Before I left I turned the thermostatat down all the way as usual before I left.
    When we arrived and opened the trailer the blower was on. I don’t know how long it had been on. I finally opened the circuit breaker panel and shut the circuit off. This circuit also handled the trailer ceiling lights and several outlets.
    I was going to turn the propane on and see if the heater would fire up but was reluctant too. It was extremely cold so we had to get a room at a local motel.
    The next morning we returned and when I turned on the circuit the blower fan went on again so I re-shut off the breaker.
    Later that day after installing anti-freeze in the water lines I had to open the circuit to turn on the water pump. This was the same circuit as the blower. When I re-set the circuit breaker this time the blower fan did not come on.
    My first thought is that it might be a faulty thermostat, which I plan to replace to see if that’s the problem.
    My questions are:
    1. Could a bad thermostat be a reason for the blower fan to just start on it’s own?
    2. I didn’t get the name of the furnace before we left (5 hours away). Can any thermostat be installed? The type I have has a lever on the botton but it does’nt seem to move so I never really touch this lever. The lever at the top sets / regulates the temperature and this is what I use to turn the heater on and off.

    Comment by ak — October 17, 2009 @ 9:18 pm

  183. Hi Chris,
    I have an early 90’s model suburban sf35f. My problem is that the burner will not light now. I can smell propane out the exhaust and i can hear the igniter try to light. It was working last year but we had a problem. we had to open the steel cover on the furnace housing to relieve pressure/vacuum and it would light. With the cover on, it would not. now the burner wont light at all. Cleaned everything i could inside. I originally had to replace the blower motor and also replaced gaskets. one of the gaskets to the blower assembly was damaged but not bad. Any suggestions? Thank you and appreciate the help

    Comment by Kyle — October 18, 2009 @ 9:26 pm

  184. Your problems sound as if I wrote the paragraph. My Amana is seven years old and I have a problem every year – -chip board etc, and service calls. Where do you get sevice for Amana without paying outragous price.

    Comment by Anonymous — October 19, 2009 @ 2:06 pm

  185. how does the auto button on a thermostat work… when does it come on when you set it to a certain degrees. if i set it on 75. then how does this work. is it best to leave it on on or auto… im concerned on my heating bill this winter..

    Comment by Anonymous — October 24, 2009 @ 6:48 am

  186. I have a RUDD UGDG_ series FURnaces with hot surface ignitor and I can’t get the bunner to come om ,the fan come on and the switch click on but the the bunner still wont come on , why?

    Comment by sli — October 24, 2009 @ 12:46 pm

  187. Yes send a picture to go with my comment

    Comment by sli — October 24, 2009 @ 12:48 pm

  188. Hi! I have a Hydroflame 8535 III — it is the model with an extra ventilator board, which they no longer have parts for. I replaced the motor and Atwood gave me direction how to rewire it to bypass the ventilator, but after many arguments with them, it just wouldn’t work. So I hooked it back up how it was and it went for a couple years, except the fan had to be on high nonstop–there was no more automatic on/off. Anyway, last year the main board went, replaced that–everything back to normal (besides no auto). This year, the fan shut off while the furnace was still hot and wouldn’t come back on. While testing (or pretending to) I crossed the prongs of my tester whlle they were touching the top and bottom relay forks and the fan turned on. I thought “voila!” the relay is bad, and/or the thermostat. So put new ones on. Then wired again the way Atwood said to because the new thermostat is not for ventilators….and still doesnt work. When I turn on the new thermostat, the furnace actually keeps firing and trying to start, but the fan doesn’t even try to come on. Back outside, and jump the relay and the fan starts right up. I don’t get it! Do you???? :)

    Comment by Jessica — October 26, 2009 @ 4:55 am

  189. I have a suburban furnance in my RV that when I set the thermostat below 60 it will work fine – cycle on and off like it is supposed to. However, when I raise it above that it will give a popping sound, almost like a cough. It appears to be at the temperature to cut off because all I have to do is touch the thermostat and it will click. I have had it in the shop two times and they can’t seem to find a problem. I need some help with winter coming.

    Comment by Anthony — October 26, 2009 @ 8:08 pm

  190. I havea suburban nt30 furnace which was running great until I left the thermostat set at 50 and the RV in storage this fall during a cool spell. On returning a week later we found the blower motor running slowly and the battery voltage very low. Now after a good battery charge the furnace runs through the normal cyclw but will not ignite. Any suggestions as to what to look for? Idid note the blower air flow seems week. Also I had a full tank of propane and on return we had about 1/3 a tank left. So I assume the furnaceran until the battery level got too low to allow ignition. Thanks

    Comment by tom — October 28, 2009 @ 7:25 am

  191. check for a wasp nest in the exchanger

    Comment by Anonymous — October 28, 2009 @ 4:28 pm

  192. My furnace runs and you can hear the fan kick in but it wont blow through the ducts. The house stays somewhat warm but can figure out why it wont blow. This furnace has been replace a couple of years ago and this model doesnt have a pilot light. So what could be causing the lack of air flow?

    Comment by Syhann Fulton — October 29, 2009 @ 12:50 pm

  193. I have a 2006 Keystone Outback, and it has a Suburban gas furnace. Last year it quit working, the blower would come on but it would just blow cold air, and I could here a clicking noise as it were trying to ignite but it wouldn’t. I blew out the out take valves on the outside of the RV with a portable air compressor and it started working again, but after about ten minutes it started blowing cold air again, and I still here the clicking noise as if it is trying to ignite. Any suggestions?

    Comment by Bernie — October 30, 2009 @ 6:13 pm

  194. I have an atwood model 8535-iv-dclp the fan comes on fine but no heat it fires up and shuts down fires up and shuts down with in seconds help help

    Comment by william — November 3, 2009 @ 5:04 pm

  195. You seem to be the man on this subject, however, you have specified that you do not cover mobile home systems…I’m hoping you might have gained some knowledge in this area, or failing that , might be able to refer me to someone that might help with a propane flow problem. The tanks are full, the furnace has a new thermocouple, however the system ran dry of propane last year and since then I have had the tanks filled, but I cannot get the pilot to light, with direct flame, (bbq lighter) and there was a cold winter in the interim., (posssibly freezing moisture in the lines?). now it is summer…ish, tho the system will still not light…I believe that this is not an issue with flame level, (tried to light with the aforementioned lighter), Could it be a regulator issue, or the furnace “controller” it is an old intertherm, (very old, firebox in good shape).
    Locally, the cost for a “professional” is $137.50 per 1/2 hour, so as you might understand, I would like to get this done uhhhh, myself, with alittle help from my friends…


    Comment by Chris — November 8, 2009 @ 10:06 pm

  196. Chris,
    I have a SF-30. The unit ignites, burners run for a few seconds, then go out. Tries to ignite 3 times then quits. Voltage & tank pressure seem good.
    I shorted across the limit switch, still the same problem.
    Any suggestions?
    Thanks in advance,

    Comment by Glenn — November 9, 2009 @ 7:42 pm

  197. i have a coleman propane furnace with a coleman thermostat to got with it but the problem is the thermostat is not adjusting right it slides all the way to 75 and 80 at the top of the scale the furnace runs good when it runs it is a mach thermostat what is the problem thanks john

    Comment by john — November 10, 2009 @ 11:49 am

  198. Chris, I have two Carrier Air V units on my camper. One unit is a heat pump. I was operating with the heat pump unit and woke up very cold. When the heat pump quit heating because of the outside temperature the furnace did not start. I tried to start the furnace with the other unit and it did not start from the thermostat in the unit. I first thought I had problems with the igniter in the furnace. I had someone operate the units and listened for the sound of the pilot light starting. No sound. Then I depressed the emergency start button on the HP unit for the required 5 seconds and the furnace did start. I then checked the other unit and it did also. My thought was that I had a bad thermostat but it is not usual for two to go at the same time. Then I saw some thing in the service manual about raising the temperature 10 degrees above room and waiting for a minute. My camper is two hundred miles away so I will not get to experiment again until Wednesday. Do you have any suggestions?

    Comment by Alex — November 10, 2009 @ 12:59 pm

  199. Hi Chris,
    I’ve been reading the great advice you’re giving to others and I was just wondering; can you help me find a website that can help me with the kind of furnace I have, troubleshooting, cleaning maintaince etc. All I really know is that it’s a 119 series gase fired furnace. I don’t really see a brand name on it, but when I had it serviced I’m told get rid of it and get a newer furnance. The people that service is also nthe people that selling them as well. Waht’s your advice? Thanks!

    Comment by Magnolia — November 11, 2009 @ 6:18 pm

  200. Hi Chris,
    I’ve been reading the great advice you’re giving to others and I was just wondering; can you help me find a website that can help me with the kind of furnace I have, troubleshooting, cleaning maintaince etc. All I really know is that it’s a 119 series gas fired furnace. I don’t really see a brand name on it, but when I had it serviced I’m told get rid of it and get a newer furnance. The people that service is also nthe people that selling them as well. What’s your advice? Thanks!

    Comment by Magnolia — November 11, 2009 @ 6:24 pm

  201. Sounds like Suburban should have recall on these!!! We have the same problem.

    Comment by John — November 11, 2009 @ 6:57 pm

  202. I find your site very informative as to troubleshooting furnaces. I just want to pass on
    a little tip. My furnace would blow the fuse when changing the thermostat to Heat.
    I took the furnace out of my camper to trouble shoot it.(SF 30) The fan motor would not rotate. This was caused by a very large Dirt Dobber nest inside the combustion
    Fan. It was really set up like baked clay. I finally got it out and ops checked the blower motor, it ran good. Had I put some duct tape on the air exhaust port on the
    outside of the camper when not in use this would not have happened. Just a thought. Thanks for what you are doing to help people.

    Comment by jerry. — November 14, 2009 @ 8:58 pm

  203. OK this is long so I’m going straight to the point.I’ve read a good many of the comments on Furnace Problems.Symptoms:Circles and starts and shuts down as many others have experienced : So Far I have cleaned the heat exchange and fan area,replaced the High Temp sensor,Check’s burning camber Clean,checked starting system and cleaned all parts,adjusted electrode to specs.I have read in several furnace repair forums all of the above and depending which one you read they included the circuit board,sail switch and thermostat.OK what i get from this is basically you end up rebuilding the hole furnace if you guess what to replace first.O did i mention i also replace both batteries they needed it and the propane regulator.Also i have got it to run on three occasions in the last 2 weeks for up To 8 hours shut it of and the problem starts all over.Frustrating you know what i mean!GOOD NIGHT ALL

    Comment by Joe — November 14, 2009 @ 9:45 pm

  204. We have a Suburban heater in pop-up camper. We always run on electricity, not battery. It has been working fine for several years, but this weekend the flame would not ignite. The fan blows, I hear a click sound as though it’s trying to ignite, but no flame. I just happened to hit the breaker for the DC. The igniter lit! It runs fine, warm air, and when it reaches the set temp shuts off like it should. But when the temp cools and it tries to kick back on, no flame. Press the breaker and it lights again. Unfortunately, I can’t do this all night long! My husband, Mark, took the unit apart and cleaned it. Put it back in and still same problem. What should we check or replace next?

    Comment by Patty — November 15, 2009 @ 3:00 pm

  205. I have a Coleman Evcon furnace Mdl 2DLASO56BDF in my mobil home. It started blowing cold air. Do I need to call the repair man or is this something I could trouble shoot.

    Comment by Jo — November 16, 2009 @ 5:27 pm

  206. Hi,
    I have a carrier furnace that is acting up.
    I changed the thermostat batteries (Honeywell) Programmable heat/cool type.
    The furnace is not turning on when the thermostat temperature setting goes under the set programmed temperature.
    Sometimes the furnace will start to light and then prematurely stop and turn off.
    If I turn the electronic kill switch (on/off) switch the furnace will heat up and start blowing heat.
    Any suggestions you may have would be great.
    Best Regards

    Comment by Dave — November 17, 2009 @ 8:40 pm

  207. Hello I have a miller mobile home furnace. When it first kicks on it spits sputters and rattles & rummbles; sometimes for almost a minute, Not everytime probably 80% of the time. Can you possably tell me what is causeing this ??

    Comment by clyde460 — November 18, 2009 @ 5:57 pm

  208. I have a Dometic (Suburban i think) furnace SF-25F. It has been working fine for the past cold season but when i tried to fire it up today it keeps blowing the 15 amp fuse. The thermostat works both the roof AC unit and the furnace. If i turn on the heat it will be ok until the furnace tries to start then the fuse blows. The AC will run properly before the fuse bloes however. Promised the kids a camping trip but it is getting to cold to go without heat. HELP

    Comment by craig — November 21, 2009 @ 11:56 pm


    Comment by BRENT — November 22, 2009 @ 9:46 pm

  210. I have a suburban nt40 furnace my problem is – I set the thermostat the unit kicks on it will blow hot air for about 3 or 4 minutes then the heat shuts down (not reaching temperature), but the blower keeps running.. The unit I think is 10 years old, but everything looks new I have replaced the circuit board, blower motor and both limit switches also replaced the power converter… Please help..

    Comment by Scott — November 23, 2009 @ 1:04 pm

  211. I have a furnance that seeto work well,but it only gives off luke warm heat. Please helpe.

    Comment by Anthony Estres — November 25, 2009 @ 1:57 pm

  212. I have a SF30 Suburban furnance in my motorhome. I can’t get the blower to kick on, so I took it to the rv dealer where I bought it. He said it was the control board, so I replaced it but still no power to the thermostat. Any ideas where to look.

    Comment by Mike — November 26, 2009 @ 11:54 pm

  213. My propane furnace will not keep the pilot light lit after it is finished running. It will make a click sound and the pilot will go out. I just changed the thermocouple two days ago and it did not solve the problem. Any insight will be greatly appreciated. Thanks your words my problem~ what fixed it?

    Comment by Anonymous — December 1, 2009 @ 12:58 pm

  214. i have an hydro flame 8535 ll furnace. the internal circuit breaker keeps tripping. it will run fine sometimes for 5 minutes, then will trip. sometimes for much longer periods…. but it always trips the internal breaker. do you have any suggestions of the problem.

    Comment by sam — December 2, 2009 @ 5:43 pm

  215. I haave an intertherm furnace in my mobile home and the pilot will not stay on

    Comment by james taylor — December 3, 2009 @ 10:10 pm

  216. Ii have an intertherm furnace in my mobile home and the pilot will not stay on

    Comment by james taylor — December 3, 2009 @ 10:12 pm

  217. hi all
    i have 85 winnabaggo lesharo. the heating unit is a suburbian. on the area of the lp tank there is about 7 or 3/4 of a tank of lp in there. there is also a gage in the same area well the same gage that says i have the same amount of water. i just bought this in may of this year thinking my wife and i would spend the rest of our lives traveling, we are retired. unfortunetly she passed in august. sadest day of my life!!! ok enough about me. in the summer i checked out the heating and stove and both were working fine . i again tryed it out in september. working just great. this past saturday i went to the mountains w/some old freinds. pulled in about 3:30 pm (we live in pittsburgh, pa. it was about 50 outside but i thought im better check the heater again… worked fine. great news cause i new it was going to get cold that night we had pleanty of gas or lp. about 8:00pm we tryed to get the furnace working and all the electrical equipment worked fine but i got no heat what so ever. went outside to find that i now had no lp gas. grrrr.. i just checked it hours before. but nothing it was about freezing that night .we all bundled up in double sleeping bags and we made it thru the night. about noon it started warming up. so i went outside to check to see if we had lp gas!!! and we did. fired up the furnace , the stove burners. ohh yea we were in biziness again. about 7:00pm the temp droped again ,cold cold… the heater would not work again. stove either. my question is !!! is there anyway the lp gas could have frozen. this was a rv i bought in florida and i never filled the lp tank seeing that it had sooo much in it. dumbfounded and confused. my kids and i like to get away evey so often,,, well not exactly kids they are in there very late teens and one is in iraq. he is coming home for the holidays and i would like to take him away from all the insanity he has had to deal with. going rving is just the way to do it but lets face it w/no heat, it wouldn’t happen. any help or info would be much appreshated

    tom o
    thank you in advance for any input you can give

    Comment by thomas ortlieb — December 4, 2009 @ 1:49 am

  218. Hi. I need help! Heater won’t blow air up b/c thermostat isn’t working correctly. And I DON’T Have the $$$ To hire an electrician/heater man. I did play w/the circuit bored and discovered the the red wire is disconnected on the bottom. When I touch it to the “Sprialed/Coiled up” metal, the heat goes on.
    Do you know where the red wire was supposed to be attached to, on both ends???

    Thank you SOOOOoooo Much for your help!!!
    It’s gonna be a COLD Nite!!!


    Comment by Vikki — December 4, 2009 @ 10:55 pm

  219. Sorry! Me again. Guess it’d help to tell you what kind of thermostat it is.

    Hunter Fan Company
    Model # 40020A – 350

    24 VAC or Millivolt Systems
    1 amp maximum load

    Thanks again!!!

    Comment by Vikki — December 4, 2009 @ 10:57 pm

  220. Our forced air propane furnace system acts up from time to time (today!). The heat did not turn on at all last night (set at 64, went down to 57 by the time we woke up). I can manually raise the temperature on the lcd thermostat screen…and the furnace will wake up as in normal operation, but when it comes time to perform it doesn’t blow any air at all. It just goes back to sleep. This happens two or three times per season, and has always fixed itself. The repairman came last year, but the system was working again by the time he opened it up – said we would have to just wait until the next time it happens. Any likely causes!? I suspect it will work again before I could bring the expert in.

    Comment by Steve — December 6, 2009 @ 8:59 am


    Comment by TERESA CANNON — December 6, 2009 @ 11:20 am

  222. Hi , I have a ’89 Lance with a Hydro Flame heater with a White-Rogers wall thermostat. It seems to work fine,,,,But It turns its self on in low temps(30-40) & runs the battery down….??

    Comment by Rick — December 9, 2009 @ 10:50 am

  223. I have had a strange situation happening to me. I have a natural gas furnace that is located in the loft of my home. My heat will run most of the time and it is fine. A couple of times the furnace has kicked off and will not kick back on. I have tried to manually override at the thermostat, but it will not override. The only way is to get my ladder and go in the loft, flip the furnace disconnect switch to the off position and then back to the on position. Then magically it fips back on. this would not be so bad but my loft is difficult to get into. This is my first year in this home so I am not sure if it has had this problem in the past….can anyone help me with this?

    Comment by Kevin — December 10, 2009 @ 11:05 am

  224. May be able to help you..very knowledgeable on Mobile home Coleman and Intertherm/Nordyne elect and gas furnaces.

    Comment by DAN — December 10, 2009 @ 4:15 pm

  225. You may be able to troubleshoot it.yourself. Depends on what the symptoms are. Main difference between Mobile Home and Residential Homes are the Heat Exchangers (Mobile homes have Sealed Combustion Heat Exchangers, which mean they get their combustion air from outside the home.

    Comment by DAN — December 10, 2009 @ 4:20 pm

  226. could be hard ignition.(not too safe). Also could be the heat exhanger expanding. After start up, does it seem to run fine? If so, they make a repair kit, that keeps the heat exchange for rumbling. So furnaces have a baffle at the top of the furnace, this could be loose. Miller/Intherthem-same Manufacturer.

    Comment by DAN — December 10, 2009 @ 4:24 pm

  227. If pilot goes out when you release the button/lever, only two or three things it could be. Make sure the top 1/3rd of the thermocouple is in the pilott flame.(inside the flame) If so replace the thermocouple first(cheapest). After that, it would be the valve. If it goes out once in awhile, then it could be a few things. Weak pilot safety in valve(have to replace valve), wind conditions, etc…

    Comment by DAN — December 10, 2009 @ 4:29 pm

  228. Why is my heating furnace making popping noises after the fan comes on and after it shuts off? Is there any way to correct problem? A response would be greatly appreciated.

    Thank you in advance.

    Have a nice day

    Comment by Huguette — December 17, 2009 @ 6:58 pm

  229. I have an thermostat problem replaced old thermostat with a HoneyWell RTH111B. My wires from my furance have 4 wires a Red, White, Greem, and Blue.

    As directed by the manufacture I placed the my furnances red wire at the Rc on the new thermostat which has a jumper wire connecting the Rh and Rc, I then placed the Blue wire on the new thermometers Y terminal, the Green wire on the new thermostats G terminal, and the White wire on the new thermostat W terminal.

    I reset the furnance which included shutting breaker off and also shut off the switch box my furnance has and reset. I then turned the thermostat on and the set the fan to automatic the furnance kicked on and the blower started immediatley and the furnance ran for about 5-10 minutes and would never blow warm air and cut off.

    Next I switched the fan setting to on and the blower run all the time with cold air. What is going on with my system it is going crazy on me. Do you have suggestons.


    Comment by Ed — December 22, 2009 @ 12:10 pm

  230. I have a Duo-Therm furnace. When it comes on it blows for a little like it supose to then the gas valve clicks. Instead of the burner haveing a constint burning sound it pops and spluters then goes out. Can you help me with this problem.

    Comment by joe — December 22, 2009 @ 8:13 pm

  231. Had same problem with new RV suburbian furnace, took it to dealer and it had air in the lines. Now I have same problem again. I have to find how to remove air from the lines

    Comment by Aldis crouch — December 27, 2009 @ 3:50 pm

  232. his is john again and the only thing i can see on my coleman furnace is the model no it is a 7900 series by coleman standing gas type my other coment was on nov 10 at 11:49 am can you help again thanks john from west virginia

    Comment by john — December 29, 2009 @ 2:28 pm

  233. Hi
    I have a Suburban NT-24S furnace. When i turn the thermostate on the furnace runs great. The thing gets up to tempature and the thermostate shuts the furnace down the fan runs to cool the unit and then shuts down. When the thermostate kicks back on the fan runs then you here a click but no ignition and the fan continues to run until i turn the thermostate off. Then I pulled the front cover off and turned the thermostate back on the fan will run after the delay and then you here a click and you can see the spark from the igniter but no ignition i then turned off the thermostate again waited for it to shut down. Then I waited a few minutes and then turned it on again and the furnace worked great. It always works great when it works whitch is when i first turn it on or after i turn it off and on. I have replaced the Limit Switch, sail switch and the spark electrode with flame sensor but need to find out why it works sometimes but not all the time. Any help would great. Thank you

    Comment by Richard — January 3, 2010 @ 1:01 am

  234. Hi Richard,
    It sounds like the LP gas valve is sticking, simply because you can see the sparking, which means pretty much everything else is OK.


    Comment by Chris — January 3, 2010 @ 4:40 pm

  235. Thanks Chris for your help on my sticking LP Gas Valve. I wanted to ask if there is a way to rebuild that gas valve and if so would you know were i can get the kit to rebuild it or is the valve junk. Thank you

    Comment by Richard — January 4, 2010 @ 9:38 pm

  236. Hello, was wondering if you could help. I have a suburban sf-30f. the furnace seemed to be running fine then one night it sounded like the motor was slowly coming to a stop. So I replaced the motor…which seems to be running the way it should, thinking the problem was solved i walked away. only to find that when i got home the furnace was out again. Thinking the t-stat was no good…I jumped the two blue wires right at the unit(eliminating the t stat). furnace started up and ran…i replace the t-stat. Then I waited to run a full cycle…seems the unit it shutting down because the the gas valve is not shutting off. I think the unit not shutting the gas down to allow the unit to cool once the temperature has gotten to great(in the pellenum??). so I manually jumped the t stat(2 blue wires) again…and after letting the unit get hot i disconnect the t-stat wires and the gas valve shut off and the plenum cools and the unit shuts off the way it should. is there a limit switch causing this? or module board?? any help is appreciated…bob

    Comment by bob — January 6, 2010 @ 1:23 pm

  237. Chris, read all the problems people are having but did not see any like mine. I have a 2009 Laredo by Keystone. The suburban NT30SP furnace I have works sometimes. One night last week I turned furnace on and it worked fine, until propane ran out. I switched tanks and turned thermostat off for about 20 seconds and no response from furnace, temp set at about 75 outside about 40. All it was doing when I turned it on was 1 click and 1 click when I turned it off. Second tank of propane was full. Turned stove on to bled air from lines, stove worked fine. Need your help. Thank You.

    Comment by Harry on Wed. Jan. 6,2010 — January 6, 2010 @ 2:13 pm

  238. No need to reply, My suspicions were right. I ran the furnace again and when it was so hot that I could not keep my hand on it, I disconnected one of the wires attached to the limit switch located on the chamber. the gas valve shut off as it should(not allowing the chamber to exceed it’s allowable temp). $9.00 fix. RV place tried selling me a module for $150.00…

    Comment by bob — January 7, 2010 @ 11:05 am

  239. hi ,i have a 1996 american caravan and i am having a problum with the suburban furnace it is the 1 with cold air going in and hot air going out on a twin flue on the caravan wall out side ,the problum i have is i can smell gas when it fires up and i can smell gas all the time when it is runing if i take the front caver of and let the hot air flow throw the caravan it works well tho still smelling propain gas .and if i put the front caver back the the heater will shut down normal but will not egnite and the fans wil not shut down just continush runing ,tho my main consern is the gas i have cheked the gas feed to it ang is ok ,thanks john in the uk

    Comment by john — January 9, 2010 @ 3:34 pm

  240. I have a 30 ft fleetwood southwind storm and the furnace was working fine then the thing lights and after 30-40 sec. the flame kicks off then 20-30 sec it will kick on again it will do this 5-6 times then stop kicking on at all till I turn it off then back on then it just repeats on off again.what would make this happen?

    Comment by Will — January 19, 2010 @ 9:53 pm

  241. when we put our rv away last time we used it (4 months ago) the furnace worked. It does not work now. We did leave a light on inside the coach and ran the battery down and had to charge the battery, but other than that nothing has been done. the rv stays in a heated garage. any ideas?

    Comment by Suzy Traband — January 25, 2010 @ 9:08 pm

  242. is it possible to get a list of componants location on the furnace..

    Comment by leonard andrews — January 28, 2010 @ 3:20 pm

  243. I have a suburban NT-24S furnace. I have replaced the sail switch, limit switch, gas valve and gaskets. The unit will work at least eight to nine times restarting. During that time you can hear the gas valve click and the furnace ignites and heats up. After the ninth or tenth time the unit will not click or ignite and the fan just blows until i turn the thermostate off and then on to get it to work. When the thermostate is turned on the fan starts blowing right away and then after a short time you hear the gas valve click. Sometimes when the gas valve clicks you can hear it click hard and sometimes the click is so low that you can barely hear it. Also the fan motor is starting to make wiered loud noises like a repetative noise low and high roll. I am running the furnace on the power converter whitch seems that the voltage is changing I have a reading of 11.6 to 13 volts at the plug not while the furnace is running. Can you please Help me. Thank you

    Comment by Richard Pohl — January 28, 2010 @ 5:10 pm

  244. Replacement of the relay on a Atwood hydro flame furnace:::: An RV parts dealer sold me an Atwood Kit,Service,Relay #93849 to replace the Klixon relay #31017 on my Atwood furnace in the motorhome. I can NOT get it to work. My question: Am I correct or is there something that I can’t figure out?

    Comment by Tom Hyde — January 28, 2010 @ 5:11 pm

  245. Get a new furnace….I have an NT40 that I have put $2K into since I purchased my 5th wheel in 2006. I put yet another $350 into it when it acted like you describe above. This time there was oil in the gas valve that caused it to shut down. After repairing the furnace, I found out that the propane tank from the gas company I use had given me an old tank that had so much oil in the bottom that it soaked my lines and killed my valve in the furnace. I had to have the lines blown out 20 times to get the oil out. Everything has run fine until tonight. The dang thing has started making noise like a twin engine plane and it probably needs to be cleaned. I have had this done before, twice, and it cost me $400 each time. I think that this time around, there might be some oil residue inside the cage that has caused it to collect more dust than usual. Anyhow…I can get a new one for $635 and I won’t have to wonder any more.

    Comment by Lynn — January 29, 2010 @ 12:26 am

  246. my coleman evcon furnace has a red light that flashes 4 times what does that mean

    Comment by april parcel — January 30, 2010 @ 2:47 pm

  247. My freind has a Nordyne forst air heater.Its in a modualar home,The pilit light wont light.Its electrical.

    Comment by Pete — February 3, 2010 @ 12:26 am

  248. hey,i need some information,on my 2008 puma,i for got to claen the snow away
    from the out side vent,it back fired 2 times can you tell were the reset is or do i have to take it in and get fixed.

    tank you.

    Comment by mark — February 3, 2010 @ 1:00 pm

  249. Hi I have tha same problem that i am working thtr.I am wondering if you figured out the solution?

    Anthony Guerra

    Comment by Anthony Guerra — February 5, 2010 @ 2:12 am

  250. I have a surburan heater, It comes on, blows cold air, then will not ignite.
    I changed the limit switch, I have the ignition board but cant figure out how to change it without tearing all my walls out. I check my thermostat, blowed the dirt out, checked batteries done it all. Someone please help

    Comment by Margaret — February 12, 2010 @ 6:40 pm

  251. what could be wrong when the surface ignitor will not come on on a gas rheem furnace?

    Comment by Reginald — February 13, 2010 @ 10:24 pm

  252. i have a suburban propane heater, model NT24SP. the igniter will glow but there is no flame. the igniter will repeatedly glow then cool but the flame won’t light and the blower blows cold air. any help please?

    Comment by Andy B — February 17, 2010 @ 1:15 pm

  253. I also have trouble with suburban furnace nt34 . Fan relay , limit switch , sail switch , all work as advertised . Even gas valve works , through a test light . No power from the circuit board for gas valve , no ignition spark either .Salesman rumour that “it was working” . Bought ‘new , improved ‘ circuit board – same . No spark , no gas valve power from pc board . Sure tired of cheapo american designed @ built , crappy consumer goods . SUBURBAN MFG will probably get gov bailout . Meanwhiie , back on the farm , guess I’ll have to get a foreign furnace .

    Comment by mudman — March 6, 2010 @ 3:10 am

  254. I have a suburban dd-17dsi furnace and it just does not come on I tried the new thurmastat and still nothing it does have power to the unit no fan nothing could it be the little micro switch the the fan and thurmastat wires go to? thanks

    Comment by vince — March 16, 2010 @ 11:03 pm

  255. Hi everybody,

    I am Antoine and I am french that is why, you will maybe see english mistakes in my paragraph.
    I have done a voltage mistake today on my NT40 furnace. I applied on it 24Vdc instead of 12vdc. Blower worked fastly in 24Vdc during 15seconds and then I stopped it . Now when I apply 12Vdc it doesn’t work.

    I heard at the ignition a sound in the black relay. In the board circuit I saw 12Vdc at the blower cable (on the left of the 12Vdc input red cable). It is a red cable too.

    Is anybody know how to unlock my furnace. Is it automaticaly protected it or not?
    Is the blower motor dead? or something broken?

    Thanks per advance for your response


    Comment by Antoine — March 17, 2010 @ 6:30 pm

  256. Hello Antoine,
    The quick test would be to hook the motor directly to 12 volts. If it runs OK, then the black relay is bad (which is what I suspect).

    Comment by Chris — March 19, 2010 @ 8:39 pm

  257. Turn the thermostat to heat, and check the relay that the thermostat wires go to- there should be 12 volts on 2 leads to begin with, then after a delay, 12 volts to 3 of the leads (the 4th goes to ground).

    Comment by Chris — March 19, 2010 @ 8:40 pm

  258. Mt best guess would be the limit switch- you really have to test the furnace with it running, and not just do a simple continuity check.
    The other problem that I have run in to, which is a bear to diagnose, is that the multipin connector is bad. A couple of times I have seen the small spring contacts in them break, so they don’t make good contact with the board.
    The NT series is really a pretty good product- the main objections I have are that they are hard to service- you cannot access much with them installed, and the circuit board is too close to the heat. Dinosaur makes an extender kit which allows you to mount the circuit board outside the furnace, which answers both problems.

    Comment by Chris — March 19, 2010 @ 8:48 pm

  259. Hi, i have a 1976 scamper camper. I used the furnace last summer and the blower motor got slower and slower. Was running on 110 with a 1000w generator. Now the furnace will not work at all on 110 or 12v. The pilot light will light and stay lit but nothing else will kick in. The only thing I figured so far was I bypassed the thermostat and hooked up directly but nothing happened. Oh yeah my furnace is a hydo flame not sure of the model. Any help would be greatly appreciated.

    Comment by Raymon — March 21, 2010 @ 9:22 pm

  260. I have a hydro flame 7900-II I am getting a signal indicating limit switch/air flow problems. I replaced the limit switch and it still will not work. When you turn the thermostat on, you hear the furnace click and then 10 seconds later it clicks again and the red light starts to blink indicating the Limit switch/air flow problem. Any suggestions?

    Thank you,

    Comment by Geoff Smith — March 31, 2010 @ 3:52 am

  261. Hi Goeff,
    It sounds like the sail switch is stuck closed. On the new style circuit board which control the blower, the board doesn’t want to see power until it starts the blower, which closes the sail switch.

    Comment by Chris — March 31, 2010 @ 11:08 am

  262. Hello Chris. I have a suburban NT30SP furnace with a combo heat and A/C thermostat. The A/C works fine. When I turn the heat on the blower starts and runs for about a minute and then goes off with no heat. Thanks Mike.

    Comment by Mike — April 2, 2010 @ 3:37 am

  263. Hello chris, I have a suburban furnace, model P40. when i call for heat at the stat, the blower fan runs, but it does not attempt to light. I am curious if this model has auto reset limits, or do I have to manually reset a limit if there is trouble?

    Comment by Jason — April 11, 2010 @ 6:01 pm

  264. Hi, I have a Duo-Therm model 65925-064 furnace in my motorhome, when I turn on the thermostat, only the blower comes on, the electric LPG solenoid shut-off does not open (works fine when 12volts applied to it out of the circuit) and my ignitor has no power to it…… any ideas, would be greatly appreciated!! Cheers!! Paul

    Comment by Paul — April 16, 2010 @ 9:42 pm

  265. Sorry, I forgot to mention, with the furnace off…thermostat, I have 13.6 V on the ignitor/spark plug wire, and on the electric LPG shut-off, as soon as I turn on the thermostat, and the blower comes on, my voltages, go to 0.0 v on both. since both are controlled by a “card” I am thinking my card is bad…. Thank-you for any insight/help you can give!!!!! Paul!!

    Comment by paul — April 17, 2010 @ 8:25 pm

  266. My heater will dot start.
    I have a Atwood Excalibur 8535-IV heater in my 2004 Fleet Wood Flair motor home. I used it last week, on the first night it worked great.
    The next night it would not start, it would only make an electric buzzing noise (like a relay buzzing) for about 3-4 sec then stop buzzing. There is a diagnostic chart on the heater that you count the blinking light. The code I have is that the light flashes contentiously all the time and does not stop. This is not on the chart. My thermostat also controls the 2 AC units. Any ideas where to start checking.
    Thank you

    Comment by Mark — April 25, 2010 @ 7:01 pm

  267. I just bought a 1994 coachmen catalina, pretty nice camper. The family and i decided to do some backyard camping on the first night, so I hooked up the propane the furnace fired but won’t shut off, even when the thermostat is in the off position the fan continues to blow. the only way to stop the furnace blower is to pull the fuse. I pulled the thermostat off moved the anticipator up and down with no change. I pulled the whole thermostat off and there was ants fried to the cicuits took them off and the same thing. do i start with a new thermostat? or is it something with the furnace. the thermostat will turn the a/c on and off and to high and low but the furnace always stays on. Any help is appreciated. I guess I should mention that it is a suburban furnace with a coleman thermostat not sure on the ac unit though. Also will a house thermostat work for the RV as I can get one of them easier than the 100 mile trip to an rv dealer. Thanks for your help. Al White Jr

    Comment by Al White Jr — May 9, 2010 @ 2:17 pm

  268. Hi
    I have a Suburban SF30F furnace in my Outback that runs intermittently. We can turn the thermostat on, it seems fine for an entire day, then at some point the trailer cools down, the thermostat calls for heat and nothing happens. If it turn the themostat off then on – I can hear a click, but no fan and no ignition. Any suggestions?

    Comment by Tom — May 11, 2010 @ 12:29 pm

  269. Hi

    I’m from New Zealand and are having a little problem with my Suburban NT 30 SP heater. It’s run great for 18 years, and has just begun giving problem when starting.

    I have followed Chris excellent instructions at the beginning of this blog. And recorded 1.4amps when first switched on by putting an amp meter across the thermostat connections, which dropped quickly to .37 of an amp. Once the fan started the current reading dropped .2 amp with the bulk of the current (6 amps) being carried on the main heater feed. Once the ignition started the current reading dropped to near nothing while the ignition was running. Returns to 6 amps once the ignition stops. There is no loss of fan speed while ignition is running

    My problem is that the spark is erratic. Sometimes it is there, other times only one or 2 sparks will occur, sometimes it misses about every 10th sparks. In the clear tube besides the coil one can see sparks between the parallel electrodes.

    I have checked all wires for continuity, cleaned all contacts, cleared out the inside of the furnace checked that the dual gas valves are working. Checked the gap on the igniter, it has a more consistent spark with a gap of 3/32 than at 1/8 inches. Checked the printed circuit board for dry joints.

    Has anybody got any suggestion. Advise sure would be appreciated and what is the idea of having a neon type display besides the coil. i.e. that the clear tube with 2 parallel rods inside that have discharge between them when the spark is running.

    Thank you. Bonner Martin

    Comment by Bonner Martin — May 17, 2010 @ 9:16 am

  270. I have a sf 30 suburban gas furance and it blows cold air we tryed to chage the limit shitch but tha never helped we can hear the electroic switch trying to igniote ut no heat comes through can you tell me what i need to change ow could it be the theromsate??? or is it something with the ignioter nthanks Pat

    Comment by patricianwhitford — May 22, 2010 @ 7:51 pm

  271. sorry I just gave y0u the wrong email address see above is correct

    Comment by patricia whitford — May 22, 2010 @ 7:52 pm

  272. I have a Suburban NT Series furnace which lights up normally and heats for about 5-7 minutes then the heat starts going away until cold, but the blower continues and doesn’t shut down until i turn it off.

    What is the solution?

    Comment by Melissa — May 25, 2010 @ 12:59 am

  273. i have a wall furnace who’s pilot is still lit but wont go on. replaced thermostat and still won’t work. please help.

    Comment by Ralph — May 27, 2010 @ 6:53 pm

  274. I have an Atwood 8535 IV furnace in our RV. Intermittently (probably about once in every 10-20 starts) it will not start. When the thermostat calls for heat nothing happens. The fan does not start, the furnace does not fire. Upon removing the outside cover, the error code light indicates “Limit switch/Air flow problems”. After trial and error I found a way to get it to run again: push the reset switch which removes the error code light, and give the squirrel cage fan a flip with my finger. It instantly starts and the furnace cycles normally. Everything is fine until the next intermittent time it will not start. I’ve had it into an RV service center and of course it operated perfectly. One comment the tech had was it may be low voltage but we were plugged into 50 amp shore power during the time it malfunctioned. Any ideas?

    Comment by Jim Scheel — May 28, 2010 @ 2:54 pm

  275. I have a similar problem as jim i have a suburban furnace in my palomino and I recently replaced the duotherm analog thermostat with a Honeywell RTH7600D digital thermostat and the furnace runs great for many hours until the blower starts for 2 seconds then goes into lockout mode and will not turn on again until the thermostat is switched off and then back on. I figured it was the thermostat but after I have tried 3 different ones and it still does the same thing im not so sure. I then installed the duotherm back in and it ran 2 days in a row fine so I put the honeywell back in and same thing after 6 hours of cycling on and off fine it decides to stop running the furnace and I wake up and its 4 degrees inside my rig. The thermostat will say heat on in the lcd screen meaning the furnace should be running but its not. And when it has done this i pulled the fuse to the furnace to see what actually needed to be reset everytime the furnace or the thermostat so when the furnace quit working i left the thermostat where is was pulled the fuse to the furnace and reinstalled and the furnaced kicked on immediately! Im completely confused with whats going on any idea?

    Comment by Cory — June 8, 2010 @ 12:36 am

  276. Hello Chris,

    I have just purchased a 77 country camper with a suburban furnace. Everything worked except the Suburban NT furnace. I took it out and found burnt ground wires had them replaced and Bench tested its good to go now except when I reconnected it, wires were getting hot and blew fuse. I think that might have been original problem and re wired it all is good now except fan stays on when thermostat is off.. This is a heat only setup, do you think I need new thermostat? also when I turn sterio on fan runs faster and interior lights get brighter??? Scary

    Comment by Paul — July 3, 2010 @ 3:57 pm

  277. Chris;
    I have Carrier air v heat pumps on the coach. Went thru a T & L storm a while back but worked OK. Lately the front unit has gone crazy. AC works, then goes to furnace, and to heatpump. Turned the LP off to solve the furnace prob. Now it doesn’t start, but the green light is flashing in series of four flashes. Dont have owner’s manual, can’t get it on line. Rear unit works fine, but can’t cool entire coach. ’07 Damon Tuscany. Going to take it to the dealer when we get home. Would like to know what the flashing light is trying to tell me. Thanks Ed

    Comment by Ed — August 4, 2010 @ 2:39 am

  278. Hi, I have a hydroflame 8500 series furnace. When I turn it on, the fan starts, the green light on the board comes on but no spark or gas valve clicking. I checked voltage at the board and have 12.3v.

    Comment by tony — August 4, 2010 @ 3:49 am

  279. I have a Suburban SF series heater, thermostat seems to work fine, blower kicks in and igniter clicks but nothing happens after that and it shuts off. I dont know where to acess the furnace inside and think maybe one of the inlets is blocked, any ideas on a fix and where do I get acess to the furnace. Its from the inside somewhere. I thought it was the louvered cover under the fridge but it doesnt come off.

    Comment by dave — August 10, 2010 @ 12:24 pm

  280. My Toyota Sunrader RV with Hydro Flame furnace 8516-ll makes a noise like the fan bearing (squirrel cage) needs lubrication.

    I took the cover off, spun the fan by hand but don’t hear the noise at such low rpm.

    Where/how do I lub the fan?

    Is there another problem?

    Other comments or suggestions?

    Thanks for your help.
    Bob T.

    Comment by Bob Testerman — August 14, 2010 @ 4:17 pm

  281. Hi i have a suberan nt40 furnace that i have replaced the fan blower motor for noise and also replaced blower time delay relay and temp switch and sail switch, my problem is the furnace comes on and lites the burner and works fine for about 4 minutes and then the blower starts going slower and finally stops and burner is still lit, and it will stay on till i move the tstat down, and while it is still running you can hear the fan clicking like the breaker is opening and closing in the motor any idea where i can start with diag, i am a master auto tech so i understand electrics and electronics, but it seem that the fan motor is overheating, i checked power to the motor and it is 20.2 volts from the invertor, is that to high and if it is how do i ajust the invrtor, thanks Norm

    Comment by Norm — September 12, 2010 @ 8:02 pm

  282. also the flame goes out once the sail switch closes

    Comment by Norm — September 12, 2010 @ 8:12 pm

  283. I just bought an old 74 camper cheched regulator working properly pilot light lights when you turn up the tstat it will run for a few seconds and blow out the pilot light what could be the problem

    Comment by Brian — September 23, 2010 @ 2:47 am

  284. i have an atwood 8500-1v hydro flame furnace diAgnostic led light blinks 3 times than 3 seconds in my manual says ignition lockout fault but does not tell me how to fix can anybody please help as i am camping now.thanks robbie

    Comment by Robbie — October 30, 2010 @ 4:53 pm

  285. Chris, the amperage technique is brilliant–thanks

    Comment by David Alley — December 13, 2010 @ 11:58 pm

  286. Ist off you guys are doing a great job.!

    Now, I have a Hydro Flame 8525 and my problem is that burner does not lite every time.

    I was thinking a glow plug type ignitor and cleaning of build up possible. It has a electronic board system. I have no knoweledge or info on this. Is a voltage checkable across board to the ignitor?

    Any leads would be great and thanks.

    Comment by Mike Solomon — January 5, 2011 @ 5:40 am

  287. We just purchased a 5th wheel with a SF35 furnace and we have been using the furnace and found that we go thru the 2- 30 lb Lp tanks in about 3 days? The temp outside is around 25-35 F and we have the Arctic pkg on the 5th wheel. I do not feel much blow of heat in the center of the coach or in the bedroom, only in the rear. I do feel like a radiant heat however. Where do we start to figure out the problem? We were told the furnace should be sufficient for our 5th wheel in winter. We cannot find the window on the furnace to check the color of the flame as it is built in under the refrigerator. Any help is appreciated.

    Comment by Cheryl — January 7, 2011 @ 8:22 pm

  288. Mike- really the only way to test the spark output of the board is like testing any spark ignition wire- hold a ire close to a ground (3/16″) and watch for a spark- but trun the LP off and be careful- it’s over 10,000 volts and it can bite!

    Cheryl- most of the time an issue like this is caused by disconnected or loose duct work. It also could be that too much heat is being diverted to the tank area.

    Comment by Chris — January 7, 2011 @ 10:17 pm

  289. i have a atwood hydroflame model 8531lll that works just fine but squealls when running . do i need a new motor or can i just lube it?

    Comment by david kelly — January 10, 2011 @ 12:32 am

  290. I have a Surburban Model P30S. The unit functions properly until it seems to reach a certain temperature then starts a vibration sound and won’t complete cycle and shut down.By dropping the thermostat setting the burner will shut down and the vibration will stop.The blower will finish cycling and the unit will shut down. I cannot find a technician in this area that will service this older unit. They say parts are not available for them. I would appreciate any input you could give me for my problem. Thank you , Ray

    Comment by Ray Herhold — January 13, 2011 @ 9:55 pm

  291. Hi David,
    The motors are not built to be lubricated, though I have done it in the past. I usually have around a 50% success rate.
    If the shaft is not loose, then you could try removing the motor and drilling a small hole in each end bell, then applying some electric motor oil (20 weight) through the small holes, which will saturate the felt around the sleeve bearings. I then put a dab of rtv silicone over the hole. Others have lubricated by just running oil down the shaft, though to me that is a temporary fix.

    But- bottom line- if you want it fixed for good, then a new motor is in order.

    Comment by Chris — January 13, 2011 @ 9:58 pm

  292. Hi Ray,
    I would replace the thermostat. It sounds like it is oxidized just enough to drop the voltage- especially as the temperature gets near the set point, and the pressure on the contacts gets lower.
    You can buy a good electronic thermostat at one of the “big box” stores pretty cheaply- Hunter makes a couple for under $20. They will have cooling on them as well as heat, but just don’t use the cooling part.
    As a temporary try at a fix, you could take the cover off and find the contacts- put a business card (a plain paper stock- somewhat rough and not smooth) between the contaces and push them together while moving the card. This is to burnish the contacts to remove oxidation.
    FWIW- the P30 is still made, and parts are still available. That’s a good furnace.

    Comment by Chris — January 13, 2011 @ 10:03 pm

  293. I have a Suburban heater in my Sandpiper 5th Wheel toy-hauler. It work great when plugged into shore power or when the generator is on. The fan is extremely loud when it is running off of the batteries. Any suggestions?

    Comment by Ray Dearborn — January 28, 2011 @ 2:12 am

  294. Chris,
    i need some desperate help. my sf-30 furnace sat for about 12 years with out being used. i tried to start it earlier in the year but had little success. i used your other posts to dismantle and check the system. i finally got it working correctly after blowing it out and checking for the correct voltages in the system. it worked fine for about a month. now when the thermostat is turned on the fan blows, the ignighter lights but does not stay lit. before this problem the furnace was reaching temperature but the fan would not turn off. it would stay in the cool down mode until the thermostat was turned off. do you have any suggestions to what might fix my issues. thanks and Semper Fi!

    Comment by chris — February 11, 2011 @ 9:45 pm

  295. hi chris got a good one for you running a sf35f.but check this one out ive read your total post and answers they are very helpful but this is the problem im having if i run the furnace in tact it will not light unless i go out and kind of muffle the exhaust port a bit without burning or blowing my hand off.or it will run fine without the service plate on the front via burner and plenum can you think of a reason this might be happening. ps it ran great till i cleaned all the mud wasp nest out of it.thanks a million tim

    Comment by tim carrick — February 12, 2011 @ 1:10 am

  296. hay chris tim here again found the problem it was the burner looked like a 25 year old gas grill burner.

    Comment by tim carrick — February 15, 2011 @ 11:26 pm

  297. Hi
    I have a suburban sf-42f it was working fine put a new motor in it earlier this year then just a few days ago it stopped working at all. I have 12.9 v to the heater circuit but nothing from thermostat but the same thermostat workes tha heat pump and a/c fine. I have no way to check LP line pressure but stove and hot water heater work ok. What do you think?
    Thanks Brian

    Comment by Brian — February 18, 2011 @ 3:04 am

  298. Thank you so much for this site. I have a coleman presidential model 4322 forced air propane unit from a 1977 MiniWinnie. I have a knack for electrical work and general juryrigging; trouble is I can’t find any wiring or parts locator diagrams for the unit. I just rebuilt the thermocouple and pilot burner assemblies with parts from a 73 duo-therm unit, and cleanned the fan areas, and the coleman runs perfect with two exceptions ; not so important is that the flame is too yellow and big: more important is that the fan stops running at the same time as the thermostat is click off and the burner is shut down( hot shutdown) although firebox was quite hot after five minutes + of burning time. I desparately need to know how to locate and replace/rebuild the fan thermal relay or delay relay or whatever this model calls this part. Info on adjusting main burner flow would also help. I must fix the hot shutdown issue as I cannot run the furnace otherwise since I have pets who probably cannot lift an extiguisher, but space heaters are not much better since fur burns!

    Comment by Alec Bosmann — February 20, 2011 @ 9:19 pm

  299. Hi, I have a mid 80’s model mobile home that just the other night the electric heater stopped working. I checked everything I could check, which is quite a bit, (ie. power to unit, loose connections, open coil thermostat, etc.) and couldn’t find anything wrong. I put it all back together and just for the heck of it turned it back on and it worked, UNTIL, it got to the set temperature and it cut off like it should but never came back on again when it got cool again. I know this is a little vague, but can you give me anything else to look for. I’m no ac/heat tech by no means but am a little mechanically inclined and have worked on them before so I have a little knowledge about them so can you give me any ideas on what to check next?

    Comment by Craig — March 9, 2011 @ 6:08 pm

  300. I recently bought a 2008 Flagstaff popup camper and took it out for our first trip. The furnace didn’t work properly as follows.

    The thermostat kicked on and the blower started.
    A bit later, the burner comes on with a nice blue flame in the peep-hole.
    Before the thermostat turns off the burner shuts down for a short time. The burner then comes back on a short time later (sometimes hear audible clicks). This repeats for several cycles (the thermostat never switching off) and then the entire furnace shuts down (burner & fan).
    When this happens, the thermostat is still in the “on” position where the furnace should not have turned off. The furnace will then not come back on until I manually cycle the thermostat by moving the setting low enough that it would turn off and then re-setting it to the desired temp.

    The furnace is a Suburban and the thermostat is a Honeywell. I was told that the thermostat is not the normal one installed in a 2008 Flagstaff.

    Any ideas on what could be causing this reaction from the furnace?

    Comment by Paul — March 10, 2011 @ 6:06 pm

  301. I’m not a tech, but heres a few thoughts from experience. Craig, my 1977 propane furnace used to do that sometimes, the thermostat contacts were dirty and would not make electrical contact unless PRESSED together tightly by hand or even scraped together a bit, cleaning with alcohol and or a file might fix it (this problem is not a possibility if it is a mercury switch thermostat.
    Paul, it sounds like your furnace is cycling the burner on/off to prevent the “box” from overheating, my older coleman used to do this but it just kept running, perhaps your newer unit counts the number of times it feels the need to cool off and shuts down permanently (until manual reset, perhaps by the thermostat as you found worked) as a fire risk reducer. Overheating could be from clogged vents, bent duct hoses, weak fan, etc. If this is the case you may notice the burner cycling the same number of times before shutdown every time.

    Comment by Alec Bosmann — March 11, 2011 @ 12:32 am

  302. hi i have a 2005 pilgrim atwood furnace blower blows ignighter lights stays lit but still blows cold air

    Comment by Brian — March 29, 2011 @ 8:09 pm

  303. Have a 35′ Nash Air works fine Heaters not coming on think its the stat not sure but there are lots of ideas here to try so i’ll get back to you on this… Thanks

    Comment by Leon Trotter — April 6, 2011 @ 6:23 pm

  304. Hi
    I have a 2004 camper with a sf-30F furnace and a Dometic AC with the control panel in it. The furnace does not work at all. After reading the Dometic test procedure, I jumped each wire at the thermostat from neg. to each appliance terminal and everything worked (both fan speeds and AC), but when I jump the furnace it blows the 3 amp fuse right away. I am leaning towards a short in the control panel, but would appreciate your opinion before I spend any more money and time on this.

    Thank You in advance

    Comment by Doug — April 19, 2011 @ 8:14 pm

  305. By the way fantastic information and greatly appreciated by many people!!!

    Comment by Doug — April 19, 2011 @ 8:17 pm

  306. 87 Bounder classA suburban rv furnace NT-30S furnace was running good, ran out of propane, filled rv tank, try and restart furnace, have blower going, can see and hear the igniter working, but no light… any ideas thx Tom

    Comment by TOM — April 19, 2011 @ 8:29 pm

  307. I have a coleman mobile furnace year 1976 model 7670 need to know the steps to change a thermocouple?

    Comment by ray — May 6, 2011 @ 4:13 pm

  308. I have a 1991 Franklin with a Suburban furnace\solid state ignition. When i start the furnace ,it heats to desired temp. On the second start the furnace doesn’t start to heat and just blows cold air. So I shut it down and try it later and does the same . any ideas Pete

    Comment by peter — May 15, 2011 @ 11:34 pm

  309. We have a 1997 Viking tent trailer, with an Atwood Hydroflame furnace in it when we are plugged to AC power in the furnace works fine however we we run off of battery power the fan will run but the furnace will not ignite to blow heat. Any ideas on what would cause this

    Comment by Rick — May 17, 2011 @ 2:33 am

  310. I have a pop up camper. When I go to light the pilot light the flam comes out way to high and starts to burn things around it I get plenty fo propan there but not getting any propan to the stove and the heater win’t work. It is a 1993 Jayco Eagle.

    Comment by shannon — May 23, 2011 @ 11:09 pm

  311. i have a sf 30 suburban furnace that i replaced the chamber in.since doing so the furnace will light and heat but starts blowing cold air before it gets to temp setting,if i turn the thermostat to off and wait a few minutes and turn it back on it will go through the same process.i know the furnace is design to shut down to prevent over heating but it does not relight.

    Comment by mike reed — May 25, 2011 @ 12:44 am

  312. Hello everyone
    I just buy my first rv, 1989 southwind 33 ft. but never can ignite stove, heater and cooler. I find that the electric valve on gas tank no open, no energize, do not have 12 volts source. any idea?

    Comment by SILVERIO TRUJILLO — May 27, 2011 @ 3:44 am

  313. My travel trailer has a Excalibur 8500 furnace. Thermostat seems to be working, but whenever it is raining, it has trouble staying lit. It lights, stays on for a couple seconds, then shuts off. Seems to start on first or second try in dry weather. Strangely, just started having trouble getting my fridge to stay lit as well. Wondering if I need a new regulator, but stove and water heater are OK. Thanks for your help.

    Comment by Cathy — July 31, 2011 @ 3:25 pm

  314. I have a new honeywell thermostat RTH2410
    with Y R G W on the back of it

    I have no idea what those letters mean or what to hook them to ?

    I have the liquid propane gas sf-30 suburban furnace for my 1994 Gulfstream Conquest travel trailer.

    The wires coming out of the furnace are :
    Red 12v + DC
    yellow 12v – DC
    blue 1 says to hook to thermostat
    blue 2 says to hook to thermostat

    I will use this for FURNACE heat ONLY and not for any a/c at all.

    Any help on how to hook this up would be great.

    furnace service manual is at:

    honeywell thermostat manual is at:

    Comment by MARK DECKER — August 16, 2011 @ 3:05 am

  315. The red +12 should go to the R terminal and the other should go to W.

    — Chris

    Comment by Chris — August 16, 2011 @ 1:13 pm

  316. I have a 2008 Keystone with a sf30 that will not run with the thermostat.In the early spring it worked fine. Then during a camping trip the fuse for the furnace/fridge kept blowing.Now it does not blow fuses but the furnace does not work from the thermostat . If I remove the 15amp fuse and re-install the furnace will light and keep going even if the thermostat is turned off. I have to remove the fuse for 5 sec then install the fuse, the blower will run as normal to cool down the furnace, then it will shut off.
    It is a dual thermostat, the ac system works okay. When you turn the heat on with the thermostat you can hear a click in the ac unit witch it always did. I assume that part is normal.
    Any advice before spending $$$
    Thanks for your help

    Comment by Doug Crtichton — August 23, 2011 @ 12:06 am

  317. I have now power going to the furnace or thermostat but my furnace is hooked to the same breaker as my hot water heater and that works fine any help please

    Comment by Pamela — September 6, 2011 @ 1:52 am

  318. I have a suburban NT34SP, When the thermostat is turned on,the furnace runs fine up to the set temp, and shuts down. after temp drops the furnace does not turn on unless i turn the thermostat off and back on. if i remove the front cover plate on the furnace then it works fine, just can’t use the vent hose’s.I checked hose’s for blockage already and they are fine.
    Any advice ?

    Comment by Kerry — September 7, 2011 @ 5:05 am

  319. I have a1977prowler duo thermal gunsce hasn’t run in3yrs can u help I’ve never turned on a furnace before

    Comment by eddy — September 24, 2011 @ 4:33 pm

  320. Is there a way to delay the furnace blower from coming on too soon. It seems to blow a lot of cold air before the burner comes on.

    Comment by Linda Ford — September 26, 2011 @ 3:04 am

  321. We had an aluminum tank once and had trouble with it.

    Comment by Linda Ford — September 26, 2011 @ 2:42 pm

  322. popping from exhaust cleaned &checked everything any help would be nice

    Comment by kenneth e weiss — September 29, 2011 @ 3:37 am

  323. Have a wall propane furnace. Fan won’t turn on and can’t light pilot light. Propane tank reads 80lbs. Any idea why furnace won’t start up ?


    Comment by jon — October 5, 2011 @ 12:17 pm

  324. hi,have a problem with furnace need to know why burners are not coming on,checked the transducer no power on the out put side.the furnace is very old one homart 600 series.have radiators in the house. oh thermostat is working ok just clicks but nothing happens. please help rhd.

    Comment by rod dailey — October 10, 2011 @ 11:25 pm

  325. I have a Suburban lp furnace in my 40 foot 1994 Sierra Cobra. The problem I’m having is pretty much the same as everyone else. I need help as I do not have a mechanically mind. My furnace clicks on fine and runs through the cycle great. However, as soon as it reaches the set tempature it turns off. When it tries to click back on nothing happens. The blower blows, the igniter clicks… it does this 3 times but it never lights back up. When I go over to the thermostat I turn it off and turn it back on again and it runs the cycle great… but… it shuts off and doesn’t reignite. Please help me.. I don’t have enough money for a new furnace so hopfully with the correct and detailed instructions I will be able to fix this problem and my kids and I won’t have to sleep in a freezing camper.

    Thank you VERY much for you help..

    Comment by wibudman — October 24, 2011 @ 2:51 am

  326. I usually see this problem with standard heat only mechanical thermostats- the contacts get oxidized enough that they cut the voltage to the circuit board. When you punch the thermostat up, there is more pressure on the contacts.
    The fix for this is either a new thermostat, or at least trying to clean and burnish the contacts in the thermostat. You can usually pop the front off and see where they are- just stick a business card between the contacts, push them closed, and work the card a bit to remove the oxidation.

    Comment by Chris — October 24, 2011 @ 8:17 pm

  327. i was told to set the anticipator to the gas valve rating,which is .2 but i was also told that the furnace should cycle 5 times in an hour during heating season,at .2 the cycle is 4min on 4 min off,so that would be an 8 min total cycle x5 would be 40 min.so i moved the anticipator to .35 which makes the cycle 12 min total.which is 60 min. furnace runs fine for a few cycles then the blower runs cold air until thermostat is reset.now i have it set at .2 again and the furnace runs but shuts down without blower cooldown ,like a hot shutoff but does this every 8 min.the furnace is a suburban P30 and i have replaced the thermostat and the limit switch,also the time delay relay,i have cleaned the furnace,and all looks good,no air restrictions.let me know what you think thank you for your help.

    Comment by jeff brown — October 28, 2011 @ 4:43 pm

  328. I have been having a problem with my coleman furnace in my home. the furnace kicks on and off over and over and over, until it eventually heats and then forces air. Everything i have seen or read for it say that it is the thermal or heat sensor. well this has a “brain’ which was replaced… Now to add to this, the furnace will run fine only if the heat in the house is set to 70-80 degrees, under 70 it will just run, without igniting the gas or blowing any heat. is this a thermostat issue or is there anything else i should try to do with ther furnace. it is a mechanical thermostat, and this issue all seemed to start when we hooked up a programable thermostat. we have taken that off and have the old mechanical one hooked up and it is still causing problems…

    Comment by roy — October 31, 2011 @ 2:25 pm

  329. My husband and I were turning on the furnace for the first time in our home. We got the thing working fine! But, while it was starting my husband had a crazy panicked thought that the vent was shut (needle pointed to open!) and he turned the handle and shut the vent!! The furnace instantly shut off and now it won’t turn back on at all. I’ve reset the machine by unplugging it and even reset the breaker, but still no luck… What do I do? I would call a professional but I’m seriously broke.

    Comment by madzap — November 10, 2011 @ 9:31 pm


    Comment by Nolan — November 12, 2011 @ 11:28 pm

  331. It sounds like a lot of the bees and part of the nest fell back into heat exchanger and possibly into the inducer motor and it dosent create the inches of vacumn to open the pressure switch start there ,I hope you didnt blow into the heat exchanger plugging it up ,let me know.

    Comment by mike d — November 17, 2011 @ 2:18 am

  332. I Have an older model RV propane gas furnace coleman #4332-749. It worked well in the begining and steadly got to the point where now it will only blow cold air with thermostat set. Sometimes it will ignite once or twice and heat, but only for a short time each ignition,then fan only blows cold air after that. I can set thermotat at lower temp and the fan shuts down. If the thermostat is set and furnace turned on it sometimes lights but only for one minute and then the samething with the fan only running and just cold air is coming out. It will sometimes run through the cycles but only once. Talked with dino tech and he gave me a run down of the schmatics, and from what he seen there was one limit switch L185 #4332309 and a fan limit switch F125 #4322308and a sail switch E22 #89HY, and that all that should be on the unit,but here is where the kicker comes in, my furnace has a third unknown disc switch I found marked L195 #4328359. And the tech did not know why it did not show this in his schmatics for this furnace. Can anyone help with this problem and help me run the system down, so I can fix this thing,it’s getting colder at night.!! Please help.!! (11-21-2011)

    Comment by Mark — November 22, 2011 @ 12:09 am

  333. That is a limit switch- L195 means Limit 195 degrees. From what I see that was an alternate location up front instead of the side, and that value was used on a different pilot type model.. I cannot find anything showing 2 though.

    Comment by Chris — November 22, 2011 @ 9:33 pm

  334. Thank You Chris,
    Another with out taking out the furnace or having an amp meter is there a way to find out the current rating on this model 4332-749 coleman furnace.? The amp rating is 5.9 amps as far as I can see on the top of the case. I’m putting in the new thermostat and need to set the antisapator on the stat to match the rating.

    Comment by Mark — November 22, 2011 @ 11:18 pm

  335. The amp rating will be the gas valve current, which *might* be marked on the valve, but usually anything under 1 should be O.K.
    The 5.9 is for the whole thing with the blower.

    Comment by Chris — November 23, 2011 @ 10:16 pm

  336. I have an Atwood Hydroflame 8535DCLP furnace with a sick limit switch. It seems to be mounted behind the blower but I can’t see it and the manuals don’t show any detail about its location or replacement procedures. I’m wondering if you’ve had to replace one and if so if you can advise me about replacing it.

    Comment by Nat — December 10, 2011 @ 7:10 pm

  337. We have an RV furnace that is allowing CO into the camper. I’ve read that in such cases the furnace needs cleaning, but doesn’t go into any detail about how to do that. My husband is looking at it today to see if there is any visible problems. If he doesn’t find anything what is our next step. We just got finished enclosing the underbelly with insulation to keep it warm through the winter so we will not be moving the camper anytime soon. Is there instructions somewhere on how to clean these? It is a hydroflame furnace.

    Comment by Ruth — December 12, 2011 @ 4:16 pm

  338. It is behind the blower, but it’s not too bad to access. You need to remove the black plastic blower cover and large blower wheel- disconnect the power, remove the circuit board on the left hand side (loosen the wing nut, pull the wires and it slides out), Remove the cover mounting screws then I usually either pull a couple of wires off to let me swing the blower cover out of the way, or remove the screws holding the relay to the cover so I can move the cover out of the way. Remove the blower wheel and you can get to the limit switch.Atwood 8500 series.

    Comment by Chris — December 12, 2011 @ 7:23 pm

  339. Hi Ruth- I would really recommend having a pro look at it. The furnace is a sealed unit, with no openings to the inside, so if it is producing Carbon Monoxide, it really needs to be carefully inspected to make sure all gaskets and the combustion chamber are intact.

    Comment by Chris — December 12, 2011 @ 7:28 pm

  340. Thanks, Chris! That’s just the kind of info I was hoping for!

    Comment by Nat — December 13, 2011 @ 1:23 am

  341. Chris wanted to tell you I replaced the control board with a new dino board and clean’d the limit switches and put in new t -Stat. Well it started right up and has been working fine ever since. I just figured since it was an old unit like 30yrs old I’ll just go the mile and it worked out great. cost of repairs, cost around $199.00 and that was for new board,extra limit switches for future use and new sail switch as well for future use as well as T-Stat so I’d say not bad instead of paying for a new unit which could of cost me around $800.00 and up. I thank you for your help,your advice helped me to narrow down the problems and now we a good working furnace. The only problem now is the cost of propane these day’s LOL.!! Thank You once again. Happy Holidays. From Mark (Warm and Cozy)

    Comment by Mark — December 13, 2011 @ 1:32 am

  342. The temperature on my thermostat goes down (colder) when my gas furnace turns on. The furnace is running unusually long to get the thermostat temperature back up to the heat temperature setting. Once I manually turn the furnace off by lowering the heat setting, the temperature on the thermostat increases once again. Is this an air circulation problem?

    Comment by Mark — December 27, 2011 @ 6:10 pm

  343. What if my thermostat is set for 78 but the house temp is 59? I hear my furnace on but my home is cool.

    Comment by miss flo — January 10, 2012 @ 2:32 pm

  344. You have a bad contactor.

    Comment by Kenneth — January 19, 2012 @ 9:22 pm

  345. I have a 1985 Sunline camper and the furnace in it looks to be an Atwood. I can light the pilot light and start furnace and it will work great. When the camper gets to set temp blower shut off and blower continues to run, when the camper cools down burner fails to relight but blower will start up and blows cold air. I have lit pilot back up and it will continue to do the same thing. any suggestions Thank you

    Comment by Gilbert — January 29, 2012 @ 8:47 pm

  346. I have atwood hydro-flame 85-11 35 series furnace that starts up and fires with no problem but will not shut down, it just keeps running. if i shut off the thermostat it still keeps running, I have to shut down the power to it to get it to shut down.

    Comment by Gordon — January 30, 2012 @ 7:18 am

  347. i have a 1998 33ft Thor chateau 5th wheel with a Atwood furnace 8535 lll i just replaced the blower motor and d blower fan put it all back to gather and the heat worked fine.since it was getting cold i would turn the heat on about 2 times a week and let it get hot in the trailer,i let a few weeks go by without turning the heat on .i went today to turn on the heat and i had nothing,when i turned on the heat i heard a pop went and checked the reset button and the fuses all were fine. im new at the RV thing,but im a mechanically inclined.can you give me any suggestions.thanks for your time.

    Comment by lenny — January 30, 2012 @ 7:37 pm

  348. If the pilot is large enough and the burner is clean, that problem is often caused by a hole in the chamber or a bad gasket- allowing air flow where it should not be. A thorough cleaning and inspection should really be done on that- it is over 25 years old, after all.

    Comment by Chris — February 1, 2012 @ 9:29 pm

  349. Hi Gordon- if the burner shuts down but the blower keeps going, it is the time delay relay. If the burner stays on as well as the blower, the problem is in the thermostat circuit.


    Comment by Chris — February 1, 2012 @ 9:32 pm

  350. I would start at the furnace and just trace the power back to see where it stops.

    Comment by Chris — February 1, 2012 @ 9:37 pm

  351. My furnace kicks on the fan comes on right away the burners light but it never puts out heat ?

    Comment by susie — February 26, 2012 @ 3:55 pm

  352. I have a Fleetwood Cobalt pop-up trailer (2007) with a Atwood Hydro Flame Furnace. The trailer is lightly used a few times a year and I have kept in good condition. The heater has always worked for us. However the last trip we took the heater was non responsive (no blower, no heater, no nothing). I have checked all the fuses and breakers. This problem occurrs whether running on the battery or plugged into the house. Just a bunch of nothing. I don’t “see” anything obviously wrong with the thermastat. From what I can “see” all the connections appear to be good. Any ideas before I have to take it in for a tech service?

    Comment by Rich — February 28, 2012 @ 8:17 pm

  353. I have a tempermental wall heater. It comes on but then goes off by itself and I have to push the reset button to make it come back on. Sometime it will stay on for 5 minutes, sometimes for an hour. Sometimes it will come on and immediatly go off. Any ideas what the problem is? Please advise.

    Comment by Kimberly — February 29, 2012 @ 9:44 pm

  354. I have a hydro flame Excalibur 8500 ll series furnace in my 1990 Motor Home. Just purchased, unable to get furnace to ignite. I have power to the limit switch and the blower runs. any suggestations?

    Comment by Bill Younkin — March 1, 2012 @ 5:16 am

  355. Probably a sticking or dead sail switch–it’s located inside next to the blower and has to respond to the air moved by the blower to show that it’s safe for the burner to come on.

    Comment by Nat — March 1, 2012 @ 4:18 pm

  356. I walked by my trailer and heard something running -it was the blower motor for the furnace.The thermostat was in the off position.The only way I can shut it off is to pull the fuse ,I even tried disconnecting the thermostat.The furnace is a suburban model # sf-25.Everything was fine two days ago

    Comment by Wayne Slahor — March 29, 2012 @ 11:20 pm

  357. I have ’98 printer withaduo-therm furnace.when I turn up the rthermostatthe fan will
    come on but the furnace doesn’t heat

    Comment by Dan Bueckert — March 30, 2012 @ 3:37 am

  358. The thermostat is dissconnected and I checked the wiring -it is not shorted -is there a way to trouble shoot the fan control module.I hate to replace a $100 part just to trouble shoot

    Comment by Wayne Slahor — April 2, 2012 @ 3:07 pm

  359. Can get igniter to click once by crossing blue wires. Still no flame. Could it be thermostat or igniter, lack of fuel???

    Comment by Robert petersen — May 1, 2012 @ 1:05 pm

  360. Heater will click but no fire

    Comment by Robert petersen — May 1, 2012 @ 1:09 pm

  361. I have an Atwood FA7816. It starts up fine, appears to go through a cool down phase, but when it tries to relight I get a backfiring that happens several times before it finally relights again. I have replaced the limit switch, adjusted the electrode, and thoroughly cleaned the unit, but the problem persists. Could this be a gas pressure (or lack thereof) issue? Any help is appreciated.

    Comment by Ron — May 31, 2012 @ 12:50 pm

  362. Hi Ron,
    I’m not 100% on your model- I didn’t know they made a 16k version of that model. It could certainly be LP pressure, but If it is the FA series that I think it is, the burner is probably rusted. On that FA model as well as the old DC8200 series, the burner has a series of waffle plates in it that are plain steel, and they rust. You can remove the screws holding them in and slide them out- treat with naval jelly and reinstall, or you can replace the burner, though the prices I found are nothing short of outrageous.

    I would also look at the air intake and exhaust, as well as current draw to make sure the blower is running correctly.

    — Chris

    Comment by Chris — June 1, 2012 @ 2:38 pm

  363. My Atwood 8900 Hydro- Flame furnace short cycles. It purges for about 30 sec,- burns for 15-17 sec. -then purges again for about 18 sec. Then it will be silent for about 90 sec. and start the cycle again. It seems like the FIRST cycle after turning it on will be a burn of about 2 min. where should I start testing. I was told maybe the ignition board or gas pressure.

    Comment by Dennis — June 7, 2012 @ 5:21 pm

  364. That sounds like it is not sensing the flame, so I would start with cleaning the burner and making sure the electrodes are adjusted properly.

    Comment by Chris — June 7, 2012 @ 8:53 pm

  365. I have a suburban SF30F (year 2004). It has worked fine until now.The fan runs for about 30 seconds and shuts off and that is it, do not hear the clicking to start the flame. I am unsure how to test for what. Thermostat? Ignitor?

    Comment by jeff — September 1, 2012 @ 10:06 pm

  366. I am assuming your SF30F has a fan control circuit board, because it shuts the blower off. The fact that it only runs for 30 seconds points to a bad sail switch or limit switch- the thermostat calls for heat, the board turns on the blower but never gets power through the limit and safety switches, so it shuts off without trying to ignite. If it was trying to, but not igniting, it would run for much longer- 3 7 second ignition trials followed by 3 45 second purge cycles.

    Both switches are easily tested with the furnace in place, if there is an exterior door on the furnace. The sail switch is behind the exterior door, and the limit switch is under the interior panel on the furnace- 2 screws to remove it and the limit switch is right there. Both should have 12 plus volts in and out, with the blower running and the thermostat calling for heat. My bet would be a bad limit switch, though a lot of times the tabs the wires hook to just get oxidized- they turn black. A quick cleaning with a pencil eraser is all that’s needed in this case.


    Comment by Chris — September 3, 2012 @ 5:03 pm

  367. Our furnace board blinks 2 times indicating the pressure switch is out. We replaced it with same type 1.74 and board still blinks 2 times. We checked the W lead on circuit board and get over 30 Ma. What could be wrong? What else do we need to check?

    Comment by Bob Spinner — October 9, 2012 @ 7:40 pm

  368. the furnace in my toyhaller didnot kick in i check the thermostat it is OK my trailer 2008 weekend woriar 20 foot

    Comment by TOUMA — October 22, 2012 @ 9:30 pm

  369. We have a 2007 Winnebago View with a Suburban propane furnace. Recently it refused to light although I could smell gas and hear the igniter working. I checked the nozzle and it is clean. I found that by restricting the air intake, the furnace will light and stay lit as long as the intake air is restricted to about 1/3 normal air flow. Has anyone had that problem and can you suggest a fix?

    Comment by Dan Hendricks — October 29, 2012 @ 12:34 pm

  370. Well I have read the entries back to 2008 and my problem is not unique. I am using my friends 5th Wheel in ND and – you guessed it – the Suburban furnace blows (litterally) but won’t go. Ignightor is trying and unit cycles off per manual but no heat happening. I have already paid $$$ to mobile repair guy who gets it to work on his bench just fine and it will work once or twice installed then right back to starting point. This is obvioulsy a common problem for this unit but I did not see where anyone followed up with what their fix was.

    Comment by Sharon — November 2, 2012 @ 5:44 pm

  371. Central Heater won’t stay lit in my 1998 Terry 5th wheel.. It will light and stay lit for about five seconds then goes out and try’s to light again, but after about five times it stops trying to light and just blows cold air..

    Comment by Mitzi — November 10, 2012 @ 4:28 am

  372. Have a model number SF-30F serial number 040107890 stock number 2331 subruban mfg co. Any idea on replacement cost???

    Comment by kim crowe — November 11, 2012 @ 11:03 pm

  373. Hi
    I have an Atwood furnace Model 8525-111 DCLP in my 1995 bigfoot camper.
    thermostat is heat control only.
    Last camping trip the furnace flame started cutting out before reaching thermostat high point, fan would keep blowing cold air.
    Lowering thermostat set point until it clicks off, and then raising it again until it clicks back on will reset everything properly and it will go through the purge cycle and then you can hear the ignitor snapping and the flame lighting. Seconds after the flame lights the flame goes out. Occassionaly the flame will relight right away but will not stay lit for more than a few seconds.
    I suspected that it may be the ignitor so I took the flame assembly apart and removed it enough so I could connect a temporary gas line extension to watch the flame light and see the flame pattern. Ignitor worked very well flame did not look that great. noticed rust partialy covering most of the holes in the burner assembly so I found a drill the size of one of the clean holes and then drilled out cleaned all the restricted holes. Hanging the burner assembly out side of the camper the burner would light and stay lit For as long as I wanted it to. Put the furnace back together and exactly the same problem came up.
    Cannot see if the flame is going out or the flame sensor is just not working or the flame is being blown away from the sensor. Any thoughts? I do have a multi meter and I know just enough to be dangerous with it if you had a trouble shooting suggestion. I am going to phone for availability of a thermopile sensor while I await your response.
    Thank you very much for any info.

    Comment by NORM — November 13, 2012 @ 7:38 pm

  374. So I replaced the ignitor/flame sensor assembly. Tried again and the same problem persisted. Tries to light maybe stays lit for a few seconds then blows cold air forever. Thought it was the mother board so I took that off and went to the dealer to buy a new one. dealer tested the board for me and said it was ok. He recomended the sail switch as a possible answer. I took the sail switch 16$ instead of the mother board 200$. Put everything back together again and it now works. I am very happy. Checked the old sail switch with a continuity meter and found that it was intermittent with the contacts when flipped to the air flow position.

    Comment by NORM — November 15, 2012 @ 1:27 am

  375. Need help. I can’t figure this one out. Have a Suburban SF-35 furnace. Worked fine last winter. However the first time I turned it on this winter this is what’s happening:
    The furnace comes on fine and does everything it is suppose to do, blower sounds good and heats up fine but after a couple of minutes before it has reached the stat cutoff temp. it shuts down because my converter shuts down the voltage to it. I hooked my multi meter to the converter output and I’m getting a constant 13.8 volts up to the point it cuts off. It does not draw down. Of course when this happens, I lose my lights and anything else running on the converter. After about 30 secs.or a minute the converter will cut back on and the furnace will start back up for awhile and do the same thing. The converter works fine when the furnace is not operating. I don’t know if the furnace has a problem causing my converter to shut down due to overheating or I have a problem with the converter. It is confusing since it maintains a constant 13.8 volts up until the time it shuts off. The converter fan is blowing as it should. I took the furnace out and checked all of the connections and blew the unit out with air and found no obstuctions. I couldn’t figure out how to take the furnace apart to get into the furnace chamber to check for any obstrutions. This is so frustrating. Please help.

    Comment by Jim — December 13, 2012 @ 3:51 pm

  376. Correction. It is a SF-30 Suburban furnace instead of SF-35

    Comment by Jim — December 13, 2012 @ 4:22 pm

  377. Hi Jim,
    That sounds like a converter problem, rather than a furnace problem. The only reason it only happens with the furnace is it is a heavier load.
    A couple of things you could try- you can check the current draw of the furnace (or just put in a 10 amp fuse on the furnace circuit), but I would make sure the converter is clean, and make sure the heated air isn’t blowing on the converter. A battery in the system would also help deal with the load of the furnace.


    Comment by Chris — December 15, 2012 @ 4:36 pm

  378. Chris, thank you very much for your answer. I think I found the problem after days of troubleshooting and getting more gray hair. The ground from the converter that goes out and is fasten to the frame apparently was losing it’s ground. Sometimes I wonder who the makers of these rv’s hire to assemble them . The wire terminal was fasten to the frame with a small self tapping screw and was put on over the factory paint which was not allowing good contact. I put on a new heavy duty terminal and sanded the paint off the frame so it would make good contact. So far, I have not had anymore problems. I think a lot of rv owners would solve a lot of charging problems by checking this connection. Thank you very much.

    Comment by Jim — December 17, 2012 @ 2:47 am

  379. I have a old Hydroflame DC8232 in a 1988 Holiday Rambler Class A Alumalite. The PO said it did not work. We cleaned the ducts and pawed around in it, and voila! It is side mounted under the kitchen sink shelf and is almost impossible to see the board (or anything for that matter).

    Anyway, it has worked for a couple of months and now has stopped working. Blower comes on and stays on but no heat.

    Multimeter readings:

    Initial 1.1 and starts dropping
    15 secs .35 Blower starts
    40 secs .80 Short spike with clicks (Ignitor?) / then drops
    45 secs .23 Blower running – no heat

    * We are using “20 gal” propane tanks with an extend-a-stay and I’m going to have them refilled and see if that helps.
    * The left ceramic “thing” looks a little blackened and the wire feels a little loose. But that was the way it was before. I’ll post a picture on our blog:


    Any insight would be GREATLY appreciated!



    Comment by William — December 17, 2012 @ 3:47 pm

  380. Hi Bill,
    Those readings indicate the safeties (limit switch and sail switch) are working fine, and the clicks reinforce that. Do you hear multiple clicks, like it is firing a spark? If so, I would say the board is fine as well.
    Because the electrode is blackened, I would bet on a very rusty burner- a fairly common issue on that model.
    The entire furnace really should be pulled, cleaned and inspected, but you can pull the burner out with the furnace in place- it is attached to the front plate that has the electrode in it. Just remove the electrode and the 4 outer screws and the burner will come out attached to the plate.
    Be aware that getting it back in can be a chore though.

    Once the burner is out, you will see a set of wavy strips and straight strips of metal in the burner, held in by 3 machine screws. These strips are mild steel, and will rust quite badly. It is possible to remove and clean them (I use Naval Jelly to de-rust). I’ll try to get a picture of one to help illustrate.
    I do have the service manual for that model at http://bryantrv.com/docs.html#furnace which should help.

    At the very least, I would make sure you have a good, working CO detector.

    Comment by Chris — December 17, 2012 @ 4:57 pm

  381. THANK YOU for your reply!!! Did you have a chance to look at the picture?

    Come to think of it, I did see some evidence of light surface rust on the unit. Being under a leaky sink (from PO might just help accelerate that).

    1) I believe I hear about the same # of clicks that I heard while it was working.

    2) If I pull the burner assembly out will I have any gas lines to deal with?

    3) If the strips are corroded, replacing the unit seems like it might make more sense. According to the price list in the service manual (which I understand is OLD and prices are higher now) it still looks like this burner is less expensive than many other models. I hope you might be able to recommend someone to order it from?

    4) Yes, after we got it to fire, we still waited until our Safe Alert CO detector arrived before using it.

    I still remember my x-father-in-law who went to work at about 6:00am as a welder walk back into the house – white as a ghost – open the fridge and get a beer at 6:05 in the morning after finding the his landlord and girlfriend in a car in the garage. They evidently needed a “private place” to have some fun but kept the car running to stay warm. I never underestimate the power of CO.



    Comment by William — December 17, 2012 @ 5:45 pm

  382. The burner pulls straight out, the only gotcha is the gas manifold (pipe) with the orifice fits in to a hole in the end of the burner- and you cannot see it when you reinstall-
    DC82 burner end
    The bad part is this burner is no longer available, though you might try All Seasons Appliances- http://www.allseasonsrvappliance.com/8509.html

    Another view of the burner-
    DC82 burner

    Comment by Chris — December 17, 2012 @ 8:42 pm

  383. Thanks for all your help Chris!

    I removed the electrode assembly first and noticed that the electrode wire was loose inside the ceramic “jacket”. It turns and moves in and out about 1/8″. I read somewhere that cracked/loose wires can cause a problem. I found and ordered a replacement part. It seemed a good idea to try this first before tackling the burner.

    Yikes! Looking at your picture, I see what you are talking about. I assume this rusting is caused by water being produced as a by-product of the propane combustion? Even if the new electrode works, I think I’ll have a look at our burner and see how bad it is when we have a break in the weather. I think I have located a replacement burner so that would make the process less labor intensive.

    I’ll post again when I have a success/failure with the new part.

    Thank you for your expertise and help in understanding the functioning of our equipment. INVALUABLE!

    Looking at the start date of this post (11/2006), this looks like this is the “thread that will never end”!

    Comment by William — December 18, 2012 @ 4:19 pm

  384. Well the new electrode kit arrived today. Similar to but not exactly like the old one.


    With the 50+ mph winter winds howling outside and in near freezing temperatures, I began the operation. (Remember we are living in this ice box)

    In 10 minutes I had it installed, turned on the thermostat AND…NOTHING. No heat.

    I went back to my toolbox looking for my pocket knife to commit harikari on this Mayan Day of Doom when suddenly…

    … in my head I started hearing the theme of Jeopardy along with some little voice chanting… it’s the ground stupid…it’s the ground stupid…

    Reflecting on this, knowing there is a ground wire on this assembly and remembering the rusty sheet metal screws, I said to myself, “myself – how will this assembly ever ground with that “fluffy gasket” and those rusty screws?

    Raiding the SO’s basket of feminine war weapons I found an emery board and began to frantically scritch scratching the rust off of the sheet metal screw.s

    I reinserted the screws, cranked up the thermostat AND … There was HEAT.

    Blessed, warm, life sustaining, sweet heat.


    Chris is 100% right, the burner should and will be removed, inspected and cleaned. On a 25 yo furnace it will need attention.

    But the lesson I seem to be learning over and over in RV’s is …”it’s the ground stupid”

    Comment by William — December 21, 2012 @ 11:41 pm

  385. All troubleshooting paths seem to have dead ends and tricky curves.

    After working yesterday evening the furnace stopped working overnight. It would fire and then shut off in about 5 minutes, sometimes longer. Fan would run continually (as it always has) blowing cold air until I turned it off and back on. Now again, this morning it will not fire at all.

    The complicating item here is that we experienced HUGE winds (branches down everywhere) last night from the side that the furnace is located on. When I put the new electrode assembly in, the air was pouring in through that little square hole. So maybe the wind is/was causing a problem?

    When it calms down today I will try again. Maybe the ground helped but the next step will be to (as Chris suggested from the get go) pull the burner and clean it.

    Comment by William — December 22, 2012 @ 3:47 pm

  386. Chris, On 12/13/12 I sent you a post describing how my Surburban SF-30 furnace is shuttng down because my converter is shutting down momentarily and comes back on after a short time . The furnace works fine when it is running. I thought I had fixed it by cleaning the converter ground on the frame of the rv but that didn’t fix it. I thought the blower motor might be shorting out causing too many amps and shutting down the converter so I pulled the furnace out again the third time and disconnected the motor wires from the unit and checked for ground on each of the wires to the motor casing and it didn’t show a short on my meter. I also checked each of the wires with the meter and it didn’t show a short. So, I ran a jumper from my converter output leads direct to the blower motor and let it run for a long time and it never once shut down my converter. It only shuts the converter down when it is all back in and hooked up . Since the blower motor hot lead is connected to the control board, do you think there is a short or something in the control board to make this problem ? I never have a problem with the converter unless my furnace is running. I did put a battery back on the rv but the converter is still shutting down like before and only running on the battery until the converter cuts back on. Or, could the blower motor still be shorting out causing a high amp draw and it just didn’t show up on my meter by just checking the motor leads ? If so, why would’nt it short out when I had it hooked directly to the converter output leads ? I can’t afford to just start throwing new parts at it until I get it fixed . This is eating my lunch ! Thanks for your help .

    Comment by Jim — December 22, 2012 @ 9:29 pm

  387. Hi Jim,
    What is the make and model of the converter? Does the cooling fan work? It really sounds like the converter is overheating, and that could just be due to the furnace being a heavier load.
    — Chris

    Comment by Chris — December 22, 2012 @ 9:49 pm


    Comment by STEVE — December 24, 2012 @ 3:52 am

  389. Merry Christmas to all and ESPECIALLY to Chris. Thank you for all your help!

    Bill and Mia

    Comment by William — December 24, 2012 @ 9:29 pm

  390. Chris, Merry Christmas and Happy Holidays. The converter is a WFCO 3 – stage 55 amp., model WF8955AN converter.The cooling fan works. The converter has never had this problem until this winter when I first started using the furnace. Like I said, I hooked the blower motor directly to the converter output leads (disconnected from the control board) and it never caused my converter to shut down. But when I hook the blower motor back up to the control board and run the furnace , it will cause the converter to shut down after the furnace runs for a short while.

    Is there anyway to test the control board without having to take it to a rv shop to have it tested ? Can the control board be shorting out causing the converter to overheat ?

    Comment by Jim — December 25, 2012 @ 11:03 am

  391. Hi Jim,
    I have to say this is an odd one, but we really need to start at the basics- I am assuming you do not have a battery in the rig, and that everything is just running off the converter. That furnace is rated at 6.5 amps, which should not be enough to overload or overheat the converter, the circuit board board would quickly burn up before causing a load large enough to affect it like that.The WF8955 should handle that with little problem, unless you have a lot of other 12 volt loads.
    The only other possibility is that the board is electrically noisy, but that’s a long shot.

    I would start with the basics though- checking voltages, checking furnace amperage draw, and you have already checked the connections. For the short term, a battery would eliminate the problem, but I really still think it is an issue with the converter- I just have not had great luck with those- I hate to be a part changer, but here in the shop I would wire in another converter just to test (replace with know good), but I have a shop converter I use for things like that.


    Comment by Chris — December 27, 2012 @ 9:18 pm

  392. A belated Merry Christmas back!

    Comment by Chris — December 27, 2012 @ 9:22 pm

  393. Thank you very much Chris. I’ll keep checking. I do have a battery on the rv. I wish these rv’s had a computer like a car where all you had to do was plug a reader into it and it would tell you where the problem is. I read somewhere that there is two times that an rv owner is happy with his rv, when he gets it and when he gets rid of it !

    Comment by Jim — December 28, 2012 @ 12:48 am

  394. Have a 2003 Rv with a suburban nt -40 with a Dometic ac and heat strip. The heater started to stop making heat, after 5 or so minutes, the fan wold continue ,I could cycle the thermostat to heat strp and back and it would relite. But still moly for 5. Minutes of so, changed the regulator, and installed a Brand new 12volt battery. Changed the thermostat, now it will make heat for about 10 to 12 minutes, and stop making heat; the fan will continue to run the cool down cycle and stop. The system will not restart until you switch the function on the thermostat or cycle the thermostat down and up. I ave a high temp limit switch to replace in the am. Any other ideas?

    Comment by Charles clemson — January 13, 2013 @ 4:16 am

  395. Hi Charles,
    I am betting the limit switch fixed it. That is a fairly common failure on that particular model. The other common failure on this model is an over heating circuit board. The NT series 40k btu unit puts out a lot of heat, and the board is not in the return airflow like it is on newer designs (the Suburban SF series and the Atwood/Hydroflame 8500 series). I would highly recommend installing a Dinosaur Extend-A-Life kit. This does 2 things- gets the board away from the heat, and makes troubleshooting much easir.


    Comment by Chris — January 14, 2013 @ 7:47 pm

  396. Wow! Sure am glad to find this help for my camper. I have a 2009 Surveyor with a Suburban LP gas furnace model Series SF 20F, 25F, 30F, 35F and 42F. Don’t really know which I have. Furnace worked fine until Ihad an LP gas company come out and hook me up to a larger unit for long term use since I’m using this as a jobsite trailer and have to get thru the winter here (16 deg tonite!). Anyway, the LP gas supplier brought a copper hookup to my LP gas infeed line from my current 30# bottles, and has a 10 psi regulator attached to it. Line looks to be about 3/8 on the trailer side of the regulator, but only about 3/8″ copper from the tank tothe regulator. Anyway when hooked to the new 100# bottle, I get a high and strange whistling sound from the furnace and some obvious ignition issues with popping and other non normal sounds. Also the furnace will heat for awhile, then shut down and not come back on. I went out this morning and switched the LP feed to my other 30# full bottle and all is fine again. I can’t find out in my paperwork or even online what the recommended psi SHOULD BE for my furnace. Can you tell me please, so I have that before I call the LP gas supplier? Thanks! Jan

    Comment by Jan Poyhonen — January 22, 2013 @ 2:34 pm

  397. Hi Jan,
    The pressure should be an 11″ water column, which is about 1/2 psi. The supplier should have both a high pressure *and* a low pressure regulator on the system.


    Comment by Chris — January 22, 2013 @ 2:48 pm

  398. Central Heater won’t stay lit in my 1998 Terry 5th wheel.. It will light and stay lit for about five seconds then goes out and try’s to light again, but after about five times it stops trying to light and just blows cold air..

    Comment by Mitzi — January 22, 2013 @ 3:45 pm

  399. Bryan, Thank you so much and I will try doing that. But the furnace does lite but only stays lite for about 2 to 3 seconds then shuts off. Then it will try and light again about 4 to 5 more times but won’t . The air flow is good. Just not heat.. I did however check the gas line and make sure it was flowing good. The flame has a blue color when lite at the stove and oven.. So I will let you know if this works.. Thank you. If you can think of anything else I might be able to ck before I have to take it in and pay to have it fixed: :/ please let me know.. Mitzi-

    Comment by Mitzi — January 23, 2013 @ 5:18 pm

  400. Hi Mitzi,
    It does sound like an LP flow issue. Try watching a lit stove burner while you try the furnace. It could also be an oil contaminated line to the furnace (or crimped, for that matter).


    Comment by Chris — January 23, 2013 @ 9:20 pm

  401. Hello Chris, I did turn on the stove and the flame was blue as it burned… So I understood that was what it was suppose to look like when it was working properly. Am I misinformed? Also what and where is the oil line. I didn’t know gas control heaters have gas? Can you please explain to me in more detail so I know what and where to look.. Thank you so much for you help

    Comment by Mitzi — January 23, 2013 @ 9:42 pm

  402. I need assistance re-wiring the surburban SF-35F furnace in my 03 Montana going to the eletratech 6 terminal thermostat……..the two wires from the furnace, when shorted back will run the furnace perfectly…..I am inable to determine where to lay down the two wires on the thermostat to make the furnace work… the original wires running from the furnace to the thermostat are broken in the factory route so I run a new pair back to the thermostat… the thermostat operates the a/c as it should…….the 6 terminals on thermostat are from left to right are ,,,, +7.5… COOL…FUR….HI FAN….FAN—GRD….
    thanx for any help you can offer,,,,,Clete

    Comment by CLETE LARSON — January 30, 2013 @ 9:35 pm

  403. I need assistance re-wiring the surburban SF-35F furnace in my 03 Montana going to the eletratech 6 terminal thermostat……..the two wires from the furnace, when shorted back will run the furnace perfectly…..I am inable to determine where to lay down the two wires on the thermostat to make the furnace work… the original wires running from the furnace to the thermostat are broken in the factory route so I run a new pair back to the thermostat… the thermostat operates the a/c as it should…….the 6 terminals on thermostat are from left to right are ,,,, +7.5… COOL…FUR….HI FAN….FAN—GRD….
    thanx for any help you can offer,,,,,Clete
    Hey Chris——disregard——I think I got it figured out………Clete

    Comment by CLETE LARSON — January 30, 2013 @ 10:08 pm

  404. Hi Clete,
    That sounds like a DuoTherm thermostat, and on that setup, the furnace is actually controlled by the circuit board in the air conditioner, and the thermostat controls that. Probably the easiest solution would be to just add another thermostat just for the furnace.

    — Chris

    Comment by Chris — January 30, 2013 @ 10:08 pm

  405. I want to offer you my sincere appreciation for helping us out. Like many Americans right now, times are hard. We are full timing in our (new to us) 1988 Class A Holiday Rambler.

    When we discovered our furnace was not functional you offered suggestions based on the model and the symptoms (in this forum) of what usually fails.

    You were 100% right. Based on your suggestions and photos we fixed the problem yesterday. Even the “gotchas” you detailed we not that bad because of your expertise.

    We were getting along with a Mr. Heater Buddy Portable (for when it really got cold) but when it malfunctioned and the weather man suddenly predicted a low of 18 tonight – choices became few and instant action was required.

    You saved the day for us.


    Bill and Mia

    Comment by William — February 15, 2013 @ 2:11 pm

  406. Hi Chris
    Have you had any trouble with repeated cicuit board failure on Suburban SF-42
    furnaces ? Board # 520820. I’m on my 4th board in 3 years.
    Any thoughts ?
    Thanks for your time

    Comment by Chuck — February 25, 2013 @ 1:28 pm

  407. Hi Chuck,

    I really have not. Do they all fail the same way? Do they not do anything or just not fire a spark? I would certainly install a Dinosaur brand board, but even the original Suburban board should last far longer than that.
    I would look at supply voltage, and check the ducting for recirculating air. The SF series puts the board in the return air flow, which should keep it cool. The other issue would be if the furnace cycled on the hi limit switch often.

    — Chris

    Comment by Chris — February 26, 2013 @ 9:18 pm

  408. Hi Bill,
    Good news- glad I could help!

    — Chris

    Comment by Chris — February 26, 2013 @ 9:20 pm

  409. My Hydro Flame thermostat Model 1030 went bad. It has five wires. Two white, green,blue and a red. That thermostat is no longer made. The replacement is a two wire thrmostat. The old one had a high, low and auto for the fan and a on off switch. The new one has an on/off switch. But no additional settings for the fan.
    What wires should I use? The thermostat instructions say use the red and white wires. using them nothing happens.

    Comment by Bruce Schlueter — June 28, 2013 @ 3:29 am

  410. Hi Bruce,
    I am assuming you have a model with the ventilator- something I’m not very familiar with, but you have to remove the ventilator and change some wiring. I uploaded the instructions in pdf form here.

    Comment by Chris — June 29, 2013 @ 10:24 pm

  411. Hi,
    I have a hydro flame furnace 8500 series lp. I have a problem that nobody seems to have. The heating and blower will not stop ever!! It was over 100 degrees in the trailer and with the thermostat set to off it was still blowing hot air. Now for the details. I have a regular 2 wire atwood thermostat. pluged in 35amp electricity. The thermostat is set to off position and coldest temp. I open the lp gas and then I hear the click and the blower comes on, then another click and I hear the ignition and flame start, then the heat comes on and never stops. I tried putting the thermostat to on and low temp but still goes on. Then I tried disconnecting the thermostat and touching the 2 wires together; then the unit starts as usual ( blower and then heat) if I seperate the 2 wires THEN the unit stops after the 90 seconds cooling time. Is it the thermostat that is a problem or the relay?
    I had to sleep in a cold trailer because I thought it would be dangerous to let the heating always on and that we may not wake up ever…
    Hope you can help

    Comment by Monique — August 22, 2013 @ 8:24 pm

  412. Hi.
    Your problem is the thermostat- I assume it is a furnace only model? You can use a digital replacement for it if you like- it will still only use 2 wires. If you do go digital, just get one with batteries, not one powered by the furnace.

    Comment by Chris — August 22, 2013 @ 8:37 pm

  413. I have an Atwood RV furnace, when I turn the thermostat on the blower comes on then there is a loud bang and then the furnace lights and works fine. This will do that every time it lights…any ideas???? Thank you

    Comment by Randy — September 23, 2013 @ 1:49 am

  414. I am assuming the bang is propane igniting, and not a mechanical bang- it could be a few things, but I would start by inspecting and cleaning the burner and electrodes.

    — Chris

    Comment by Chris — September 23, 2013 @ 12:32 pm

  415. I have an Atwood hydro flame 8500-IV furnace in a 2000 Holiday Rambler motorhome. For a couple weeks we had a noise in our furnace but it continued to run and operate fine, but it now kicks on at the desired temperature but just blows cold air.
    In conventional home heaters, it would be a symptom of a failed igniter, but I am not sure what it is with this furnace. Any suggestions?
    Thank you for any helpyou migh be able to give.

    Comment by Dan Close — October 11, 2013 @ 2:40 am

  416. ihave a 1976 dou therm was running fine fan guit blowing and now wont light pilot light is on

    Comment by howard — October 31, 2013 @ 10:24 pm

  417. can anyone tell me why the furnace would be vibrating when it came on this morn? it has been working quietly and just fine till this morn and now it has a loud noise with vibration. we think it could be the motor fan going out but not sure. has anyone had this happen to them? could really use some help on this. thank you so much for any help you can give us. we are facing winter in an rv with two children and very low on cash right now to repair anything. Hope this isnt a major thing. :/

    Comment by Belitha — November 10, 2013 @ 4:07 pm

  418. A sudden vibration is most likely just something caught in one of the blower wheels, and not a major problem. A piece of foam or an insect nest can cause the blower to be out of balance. A bad motor would be noisy (squealing), and blow a fuse.


    Comment by Chris — November 10, 2013 @ 4:20 pm

  419. Hi Chris, I’ve got an Atwood 8520-III that will not light. Blower starts, ignitor, fires gas valve opens (can smell propane in the exhaust). I’ve replaced the burner, orifice, electrode, limit & sail switches and gas regulator. (I had the same symptoms before replacing any of these parts). Stove & water heater work fine (nice blue flame). If I cover the exhaust when it tries to light, it will light but won’t continue to run. I removed the combustion chamber and cleaned it out the best I could with a coat hanger (didn’t really find anything in the chamber). Looks to me like I’ve got a few options left: Blow out the gas line with compressed air, Gas valve not opening all the way, bad control board or I have an air flow obstruction that I haven’t found.

    Any ideas?

    Comment by Mark — November 17, 2013 @ 12:59 pm

  420. Chris, couple of updates on my post from above. I blew out the gas line from the regulator to the furnace and checked both coils on the valve (both read 50 ohms). Same result. Furnace won’t light. Covering the exhaust will cause it to light. A couple of times this time, it kept running until I turned it off but wouldn’t relight by itself. thanks!

    Comment by Mark — November 18, 2013 @ 1:59 am

  421. Hi Mark,

    That sounds like an LP issue- if it works when you block off some of the air, it means it isn’t getting enough propane. The gas valve normally either work or not- I’ve never run in to one that only worked partially, though I suppose it is possible. I would test the LP pressure at the furnace (that model makes it fairly easy with taps on the valve)- Les Doll has a good article on how to make a very inexpensive manometer to test the pressure at .

    — Chris

    Comment by Chris — November 18, 2013 @ 11:54 pm

  422. Thanks Chris, I haven’t checked the pressure but I did replace the old original regulator with a new one. That’s actually the first thing I replaced. What would be the solution if that’s the problem? Just adjust the regulator? Will that cause issues with the other appliances if I have to raise the pressure? The other appliances are considerably closer to the regulator than the furnace.


    Comment by Mark — November 19, 2013 @ 1:02 am

  423. I wouldn’t adjust the regulator without a manometer- they are nearly always set up correctly. I would probably closely inspect the copper tubing feeding the furnace, and reinspect and clean the orifice, just in case.

    Comment by Chris — November 19, 2013 @ 2:22 pm


    Comment by DENNIS — November 28, 2013 @ 11:20 pm

  425. That sounds like the limit switch is doing its job- it could be faulty, or there could be an airflow problem. There are requirements for the number of ducts and vents, depending on the model and btu rating. It could also be a crushed duct, or obstruction. Regardless, it should not be cycling on the limit switch, as you say, it is a safety device, and the thermal stress is not a good thing.

    — Chris

    Comment by Chris — November 29, 2013 @ 1:46 pm

  426. I have a 1979 Winnebago camper with a Coleman furnace . The furnace gets hot but when the blower kicks on it runs good for about 30 seconds then slowly slows down to nothing !!! Any ideas what could be wrong here ??

    Comment by jim Jones — December 11, 2013 @ 7:09 pm

  427. Hi Jim,

    A model would help, but if yours normally heats up without the blower running, I would suspect either the blower motor itself, or the fan switch, which on those models is a simple thermal switch. I would put a meter on the motor and see if it gets good 12 volt power. If it does, and still slows down, the motor is bad. If the voltage drops, you just need to find where you are loosing it- fan switch or simple bad connection.

    — Chris

    Comment by Chris — December 12, 2013 @ 2:16 pm

  428. I have fifty foot luxary by design it has heat strip one on each side and two lp gas on each side thermostat on each side. I tried to turn thermostat on and nothing happened no blower or nothing same on other end. Reset all breakers and no bad fuse. Outside of unit is two panel doors for heat but look self contained. Do I take panel off to turn a switch on or blower switch. Ive never had this in rv before I bought used. Yes ele heat works but would like gas option. Just dt seem like both of them would go bad. Does it have to have 12volt to work because if we shut power dn no rv lites come on. Was hoping this was something we could fix. Also battery shows ch on wall but when we take power away it shows no charge on wal. Does that mean battery bad. Thanks for input

    Comment by Tina Taylor — December 20, 2013 @ 12:07 am

  429. Hi…we have a SF30 Suburban furnace with a Dometic Control Center 2. We have been told we have to set the furnace blower to automatic. We do this and there is no air flow. We took it to a dealer and he put a kleenex over the floor vent and said it was working. It barely blew off. In our other 5th wheel, the air flow was enough to blow off a rug. This one is not. We have the same size furnace and 5th wheel. Do you have any idea what it could be? We have checked obstruction in the vents and nothing. I’m not sure how the sail switch works or if that has anything to do with the air flow. We took off the duct work directly from the furnace and there was hardly any air flow there as well. We would like to get this fixed before we start camping again in a few months. Thank you for any information!

    Comment by GARY — January 22, 2014 @ 2:21 pm

  430. I recently purchased a ’95 winnebago vectra and have a problem with the furnace. It turns on with the vehicle cold and runs for a nour or so, but then it stops heating the air. It just keeps running the fan. Where should I start looking? Thanks.

    Comment by Herschel Mobley — February 4, 2014 @ 6:56 am

  431. Chris,
    I have a Suburban SF-30 furnace in my Keystone Outback TT. It worked until hunting season started, then it would not lite. Took out & took to RV repair & they replaced the circuit board & said that fixed it. It use to have a cool down time after the heat went off of about 60 to 90 seconds. Now it runs about 10 minutes cool down time. With that the temp drops so low, while still in cool down time, it calls for heat again, so furnace gets confused so it just shuts down. My son has pulled out & put back in this furnace so much that he is wearing the paint off the case. Any way to fix this dang thing????????

    Any help will be greatly appreciated,


    Comment by Jerry — February 7, 2014 @ 7:04 pm

  432. Chris,

    I forgot to mention that even with thermostat in the off position, when re-installing furnace, as soon as you touch the power wires together (no other wires connected), the fan comes on immediately.

    Whats the deal with this?

    Is this part of the problem?

    The board they replaced at the RV place was a new after market one with a longer warranty than the mfgs. board (90 day versus 3 year).



    Comment by Jerry — February 7, 2014 @ 7:55 pm

  433. Hey I have a hydro flame 85-11 in my 91 g30 mallard sprinter. It ignites and comes to temperature, but seems like the pilot or sail switch fails to work after that first cycle… When the blower fan kicks on to bring it back to thermostat temp, the blower fan only blows cold.. Don’t know where to look to solve this one! Help!

    Comment by Joe Doviak — March 9, 2014 @ 4:36 pm

  434. Chris, I have a Suburban RPV heater in my 2007 Heartland Trailrunner that is givving me fits!!! First of all it will come on and start heating the trailer and then it will seem to go int booster mode and the lights will brighten for about one minute and then start to dim and the converter fan will also kick in. That will put the heater fan and lights at about normal. Now with the heater off the converter will kick on and off with the lights ggoing up and down in brightness. is the a problem with the converter or a grounding problem? If it is a grounding problem, where should I look first?

    Thank you,

    Comment by Zane Mohler — March 17, 2014 @ 1:31 am

  435. Hi Zane,
    I would bet on the converter. Is the battery hooked up and good? Normally, we don’t have grounding problems with furnaces, simply because the copper LP pipe provides a good ground.
    I would check the battery connections and ground though.

    — Chris

    Comment by Chris — March 17, 2014 @ 6:11 pm

  436. Hi Joe,
    If you have the furnace only thermostat, I would change that. With mechanical thermostats, what happens is when you first turn the thermostat up for heat, the bi-metal spring hols the contacts tight, but after a heating cycle, there is not as much pressure on them, so the voltage drop is too much.
    You can try cleaning the contacts- remove the thermostat cover, put a business card between the contacts, push them closed and pull the card out. This should burnish and clean the contacts.

    Comment by Chris — March 17, 2014 @ 6:14 pm

  437. Hi. I have a Dometic analog thermostat that does both the heating & cooling. It’s in a 2006 Montaineer. The furnace will properly run for a few hours, then it stops & you wake up freezing. If you push the lever on the thermostat it will restart sometimes & sometimes not. When it will not, you can hear it click at the furnace when the thermostat lever hits the temp it should come on. Am I correct this is the thermostat? Want to know before I either order & replace the thermostat or call a repair guy & he comes from a long distance so is expensive ( I travel nurse & live in this off & on since I bought it new).
    Thank you for your time.

    Comment by Kathy — March 24, 2014 @ 6:28 am

  438. If you can hear a click from the furnace, it appears the thermostat is working, and the problem is in the furnace- there are a number of things that could cause this, from bad circuit board (not all that common), to bad power to a stuck sail switch (which would cause the fan to not start).

    Comment by Chris — March 24, 2014 @ 12:39 pm

  439. Thank you! I will call the repair guy. He replaced the circuit board last winter so hopefully it’s not that.
    Thank you again!

    Comment by Kathy — March 24, 2014 @ 3:14 pm

  440. I have a sf30 suburban. it starts up fine and the blower comes on. it then clicks 3 times and turns off. a red flashing light from the board comes on and flashes 3 times. where would be a good place to start?

    Comment by Dave — July 10, 2014 @ 12:19 am

  441. Chris, I have read all of the above and I have a different problem:

    I have a DuoTherm thermostat on a Lance 2001 camper connected to an Atwood Hydroflame 8500 IV furnace and a Dometic 6204 rooftop AC.

    In Winter desert conditions (=let say 40 degrees outside), and if we set our thermostat to 60 at night, the furnace will NOT come on; however, if we set the thermostat to 85 degrees, it will cycle on throughout the night and heats the camper and shuts off, etc.

    Any reason why the furnace will not cycle on when the thermostat is set to 60?

    N.B. we never use the camper during the Summer, so the AC has never been used.

    Thank you.

    Comment by John — July 24, 2014 @ 9:40 pm

  442. This does sound like the thermostat itself is bad- that is a common failure for the standard DuoTherm analog thermostat, if yours is like this one:DuoTherm Analog thermostat

    Comment by Chris — July 25, 2014 @ 1:44 pm

  443. Yes, it is.

    Thanks for your advice. I intend to replace it with a Hunter thermostat #42995.

    Again, thanks: what I needed to know.

    Comment by John — July 25, 2014 @ 5:11 pm

  444. Good choice! That is a popular replacement/upgrade.

    Comment by Chris — July 26, 2014 @ 1:25 pm

  445. Hey buddy .
    Whee I turn my heat on the furnace will run for a Minuit and blows cold air then shuts down any suggestions thank you

    Comment by Mike — August 28, 2014 @ 7:56 pm

  446. Oh my unit is a suburban sf-35s , thanks again

    Comment by Mike — August 28, 2014 @ 7:59 pm

  447. Yes I’m having trouble w my furnace running but not putting out any heat. Was working heating really good then stopped igniting. Any solutions?

    Comment by robert gonzales — September 11, 2014 @ 5:14 pm

  448. The furnace in my Sprinter 5th wheel has burnt up three thermostats now. I have 12.2 volts on the blue wire at the furnace. When I replace the thermostat it will run for a day or so with no issues and then just stop working. I have no clue . Any suggestions.

    Comment by Bryon — September 18, 2014 @ 9:23 am

  449. Hi Chris,

    Im having problems with my furnace. Amps are good for time delay and fan start up but they continue to drop after that and the furnace never lights up. Its an electric start furnace.
    plugged in to shore power but my batteries are in bad shape.

    Comment by Brian — September 28, 2014 @ 12:39 pm

  450. Hi Chris,
    We have a Suburban SF30 in our 2010 Wildcat. We turn on the thermostat and the blower starts and it goes thru the 3 clicks but the air never gets warm and then it shuts off after a couple minutes. The one time it did warm up, it started backfiring pretty hard (sounded like someone was kicking the outside of the RV). I shut it off and it has never heated up since. It goes thru the 3 clicks and nothing. Any ideas?

    Comment by Barb — October 9, 2014 @ 4:48 pm

  451. i just need to take a moment to salute chris for his exceptional knowledge on troubleshooting and the hundreds of people that he has taken his time to HELP with repairs and with saving folks a whole lot of money

    Comment by DAN — November 1, 2014 @ 12:25 am

  452. 2003 Suburban sf 35 furnace.turn on fan comes on then you here click might fire off about 15 seconds later you here click click at the relay board on the furnace will not relight.turn off wait a couple minutes restart same thing.If it does light it will run till it cycles off.Never had any issues with it till now.stove top works ok,water heater and refrig on gas all work okay.we have a 2nd sf20 furnace in the bedroom that works with no issues.so that rules out the lp gas pressure.I removed it from the rv and set up a bench and hook with a 30 lb propane bottle and it ran over 5 minutes with no issues.while it was out I disconnected the gas line from the gas valve that goes up to the plenum,checked the orange wire from the hv coil to the igniter and removed the nut and screws and looked good,remove igniter the space to the burner looked okay and the igniter and burner was clean.I removed the igniter checked the porcelin no cracks and reassembled.Blew out the squirell cage blower housing not alot of debris.I have been repairing appliances over 45 years and this one has me baffled.I took the board and replaced it and still the same issue.My thought is maybe the igniter is not sending a signal back to the board and the board is shutting power off to the gas valve???

    Comment by monte — November 10, 2014 @ 5:58 pm

  453. A couple of things I would check- the placement of the electrode is pretty critical in these models- I have a couple of manuals on my Bryant RV service manual page– I would really recommend pulling the burner and making sure it is clean, as well as checking the orifice- I have run in to several of this model which, for some reason, tiny bugs have crawled in to the orifice, just partially blocking it (enough that it doesn’t burn right, but not enough to keep gas from flowing).
    You can test the flame signal if you have a meter that reads micro amps (I just bought a Fluke 116 just for that reason)- you have to put the meter in line with theignition cable, with a small ceramic capacitor to bypass the meter- Diagram of using a meter to sense flame in a DSI system.

    Hope this helps- to be honest that furnace model has driven me crazy more than once.

    — Chris

    Comment by Chris — November 12, 2014 @ 1:31 pm

  454. My Atwood 8531-iv-dclp furnace won’t ignite. Turn the thermostat on, blower runs for about 30 seconds then switches off. Red light on the furnace flashes once every few seconds. I was told this was probably an air flow problem, but I can’t find any obstructions. Hot water works fine, so I presume it’s not a propane problem?
    Have had other problems with the furnace in the past: It wouldn’t turn off unless I turned the thermostat to the off position. Blower would run for 15-20 minutes without igniting.
    It’s 16 degrees out, please help!

    Comment by Brandy — November 14, 2014 @ 9:56 am

  455. Should probably mention that I haven’t attempted any repairs yet (other than checking for air flow obstructions) – and the RV is on shore power so it’s not a battery issue.

    Comment by Brandy — November 14, 2014 @ 9:58 am

  456. Hi Brandy,
    Even though that is called an air flow problem, it really is just that the board is not getting power through the sail and limit switches, so it could be either one of those. The sail switch is right inside the black blower cover- the best case would be a bit of lint keeping the switch from closing. Worst case is a bad limit switch- not expensive, but you do need to remove the blower cage to change it.
    I don’t have a good picture of that model with your setup, or I could point out the wires to test.

    — Chris

    Comment by Chris — November 14, 2014 @ 1:08 pm

  457. Hi Chris

    We have a Bryant forced air furnace. It clicks to start and then the flames jump out of it and then starts to heat normally. It also now makes a very loud bang before the flames jumps out. We shut it off because it is very scary to turn it on. What seems to be the problem?
    When we change the filter and clean and wipe around it, it works fine without jumping flames but as soon as three weeks passes it goes back to the same problem.

    Comment by mary — November 21, 2014 @ 3:29 am

  458. Hi Mary,
    I’m afraid I don’t know anything about household furnaces, but it sounds like the burner needs cleaning- if the slots in the burner are clogged right at the igniters, gas has to build up before it will light- with a bang.

    — Chris

    Comment by Chris — November 21, 2014 @ 1:34 pm



    Comment by Desiraeh — December 7, 2014 @ 2:08 pm

  460. So on my thermostat for the fan option it only works on HI when you put it on LO it shuts everything down.
    Could the thermostat be the issue with my furance? Do i need to replace the thermostat?

    Comment by Desiraeh — December 7, 2014 @ 2:15 pm

  461. I am trying to fix my furnace in our RV (Suburban NT34 BW). It fires, and burns beautifully, but goes out after 7 sec. I have cleaned and repositioned the flame sensor. Do these fail?

    Comment by brian deis — December 21, 2014 @ 5:08 am

  462. I still have a situation no-one seems to understand. if the thermostat sits down with the screw tightened down on it furnace will not ignite. if I raise it up with a washer under it , it works. ????

    Comment by Anonymous — December 23, 2014 @ 3:57 pm

  463. i have a 2004 Dutchmen 31bh i had 2 wires on my power plug to arc and had to replace my end. Ever since this my heater blower turns on and will not turn off even when i turn thermostat to off. It is blowing cold air the igniter isnt working. Only way i have found to turn it off is pull the 15 amp fuse that works heater and refrigerator. any help is appreciated!!!!

    Comment by brian scarbrough — January 19, 2015 @ 12:00 am

  464. I have a Suburban SF20 rv furnace.. I checked the power and have power to the limit switch.. The fan will not run and the igniter won’t light.. Can you give me some ideas on what the problem might be??.. Everything worked fine in September.. I parked the rv and now the furnace won’t do anything.. I’ve taken the furnace out of the rv.. Do I have to have propane going to the fan to test it??..

    Comment by Don — April 6, 2015 @ 9:54 pm

  465. It all depends on whether you have a fan control board, or the fan is controlled by a separate relay- I’m figuring you have a fan control model. For this model, the thermostat closes, feeding 12 volts to the thermostat input on the board, *and* to the sail and limit switches. The board knows the sail switch should be open, because the fan isn’t running. If the sail switch is closed, and the board is getting power through it and the limit, it will not start the fan, as it knows there is a fault. If the fan does start, if the limit switch is open, it will shut down as well.
    It doesn’t have to have LP to do a basic test, but without it, it should start and try to light 3 times- after the third unsuccessful attempt it will shut down on lockout.

    Hope this makes sense!

    — Chris

    Comment by Chris — April 7, 2015 @ 12:10 pm

  466. Have same problem with both front and rear furnaces, Tiffin said it is a control board in roof top coleman mod 8535, Cannot find anybody to verify or get a part number. Tiffin said they don’t carry part and have no Part number. When I connect the blue wires at furnace the roof top and furnace both start with thermostat in off position. Puzzled and frustrated, Help, Tiffin said board controls both front and rear furnaces. Ser number of air unit is 010409287.

    Comment by Ralph Wozniak — October 19, 2015 @ 8:25 pm

  467. Hi Ralph,
    What thermostat do you have? I assume it is a single thermostat with zones. There are 2 zone control thermostats that I can find- one at this link to a pdf, and the older model at this pdf file, but everything coming on at once suggests that power is being supplied to the wrong wire- if the thermostat is getting its power from the furnace, try switching the blue wires around- one wire from the furnace is hot, the other cold.

    Comment by Chris — October 22, 2015 @ 1:55 pm

  468. I have a Suburban SF-20F furnace. The blower runs but the ignitor does not come on. You can hear it click like it is trying to light but it never does. How do we check this?

    Comment by Kerri — November 25, 2015 @ 2:56 am

  469. You cannot usually hear the ignitor itself on that model, but you can hear the gas valve make a clunk. The SF series really need to be removed for most problems and to access the burner. The main problem with that model that can be easily fixed is a bad or oxidized limit switch. There is an inside removeable cover tha has the limit switch right behind it- often simply unplugging and re-plugging it will fix a “no fire” issue. Unfortunately, if yours is trying to ignite, that probably is not the problem.

    Comment by Chris — November 27, 2015 @ 1:53 pm

  470. We had same problem. The gas regulator on propane tanks and hoses was bad. The rv tech put a test or on cook stove and it was on 2 pressure should be on 10 or so. The cook stove worked and I wondered why my oven was not baking right. It was not getting enough gas either.

    Comment by Mary — December 1, 2015 @ 5:38 pm

  471. That’s a good tip- a quick test would be to light a stove top burner and turn on the furnace. If the flame dies out- or even gets smaller- when the furnace is trying to ignite, the regulator is a good place to start.
    The only caveat is that the stove is not a great place to test a regulator- it’s OK for a quick test, but stoves have a built in regulator set at a 10″ water column, and the main regulator needs to be set at 11″, so you really cannot adjust a regulator from the stove.

    — Chris

    Comment by Chris — December 2, 2015 @ 12:49 pm

  472. Hi Chris
    Just a weird issue I have
    Sf35q works awesome but maybe a couple times a day it will not start again after running or will do a 30 sec aproxx time sometimes more or less but the blower blows and then it shuts down also locking out the thermostat. … worse the colder it gets outside
    It only has a bottom duct vent …. which found out I had to repair the ducting so all good I thought … nope still does it…. like its over heating… and limiting out
    I have ordered more side ducts to run…. another limit switch….. trying to figure out how I can safely get some cold outside air to mix with inside air to maybe cool down the heat exchanger a little more so it can get the trailer up to heat…. it’s almost a flip of the coin when it’s going to lock out …. mostly I wake up to chilly Temps. …. we have 2 300 lbs bottles hooked up
    24 and 7 baby

    Comment by Scott — December 7, 2015 @ 2:57 pm

  473. I have a 2 year old Suburban furnace model NT-30 SP that will not come on at all. Not even a sound of anything trying to work. I can get it to work when I connect the 2 wires at the thermostat, so I changed that with no luck. There are no blockages of any kind, and it is obviously getting power. I had the heat only thermostat that came with the new furnace, and replaced it with a similar one from Honeywell that still did not work. This is the first I have tried to use it since last winter, so it has been sitting awhile. Not that it should make a difference, but this is installed in an 1985 Airstream Excella trailer.

    Comment by Joe Riniker — December 15, 2015 @ 6:19 pm

  474. Hi Joe,
    It has to be a thermostat problem- if the furnace runs fine when the wires are connected together- which is what the thermostat does. I would measure for continuity across the thermostat – you should have continuity when calling for heat. Make sure the anticipator is set at the lowest level and that the shutoff switch is turned on.

    — Chris

    Comment by Chris — December 16, 2015 @ 12:41 pm

  475. John, sounds like the burner isn’t letting gas flow correctly, gas is building up in chambers due to possibly worn/damaged burner. This causes excess gas to build up before reaches igniter. Just a tiny hole in the burner causes this. That is where you here the popping coming from. Not igniting smoothly. I finally narrowed mine down to taking off the burner, and the bottom side had a penny size hole burn through it, faulty metal. Fixed my problem immediately.

    Comment by David — December 22, 2015 @ 9:04 pm

  476. Steve, many times the AC/DC converters go bad and this can only be checked by unplugging the 12V batteries from the converter and seeing what charge it puts out without the batteries hooked up to it. The first time I had this happened it read great and was extremely misleading, until I checked the output of the converter without battery backup. I have had two converters give out. This will cause the furnace to not get enough juice to trigger or stay on long. Or, the batteries themselves go bad and are not able to supply/sustain enough DC charge to support the blowers motor, the igniter, thermostat, hot water heater, and actually everything 12V in the RV that happens to be drawing current. Even the fridge command module runs off of 12V. And, yet it could be the many other other things posted on this very wonderful site, but
    the converter and batteries are often overlooked until the end. A load tester is the fastest way I check if the batteries are shot! Even a slightly loose battery cable or corroded connection has made my furnace operate erratically. As Chris has said for so many problems, the voltage is a great place to start. I hope this helps narrow it down.

    Comment by David — December 22, 2015 @ 9:52 pm

  477. Most decent converters should have an output of close to 13.6 Vdc when they are plugged into a 120 outlet, without the batteries connected of course. When they go bad they will read 0-1 V output

    Comment by David — December 22, 2015 @ 10:03 pm

  478. The heat sensors on front of most Suburban RV furnaces cause safety shut down when they get too hot. The popping from ignition of slight build up and then flames spreading beyond the burner and out further to the front of the furnace chambers causes the front to get too hot, triggering the sensors. Mine had a tiny hole on the bottom of the burner, easily missed it. Most times its as others mentioned earlier, debris or insects or mouse remains clogging some of the burner vents.

    Comment by David — December 22, 2015 @ 10:21 pm

  479. I also have had a mouse knock my large blower fan off alignment. This can cause overheat and shut down. Not to mention it also gets rather loud quickly as it goes off balance. In the Rockies, I have had 2 deere mice cost me a total of $250 getting things balanced along with a new blower fan. I keep plenty of Victor mouse traps in the cabinets by the furnace at all times! Even if I dont see one for many months, it takes just one and you are sitting in front of a space heater on a cold night.

    Comment by David — December 22, 2015 @ 10:35 pm

  480. Kenny, most likely just dirt or soot on the igniter or in the burner, or maybe even that rare batch of slightly lower quality propane mixture, being how new it is, it shouldn’t be too major. Worst case its the t-stat failing to call for the gas. Still not major. I would just grab my air compressor air gun or even canned electronic duster air and blast it clean around the burner, vents and igniter. I would be surprised if the igniter went bad that fast, but possible

    Comment by David — December 22, 2015 @ 11:51 pm

  481. My 1991 nomad,the pilot is on but when i trun on heater is just blow’s cold air,has been working fine?

    Comment by Patty — December 28, 2015 @ 9:15 pm

  482. A make and model of the furnace itself would help. On a pilot type furnace, the sail switch and limit switch would both be suspect if you get no full flame.

    — Chris

    Comment by Chris — December 29, 2015 @ 1:26 pm

  483. Do you have any information on troubleshooting a Hydro Flame Model #FA-7825DS? And know where I can get replacement parts. Mine will not ignite at all. Thanks for your help and any information that you may provide.

    Comment by Robert — December 30, 2015 @ 6:15 pm

  484. Hi Robert,
    I have the service manual for that model at http://bryantrv.com/docs2/docs/hydroflameold2.pdf– it’s a pretty straight forward design. A couple of common problems, the burner will get rusted (it has some waffle type plates that are plain steel), it doesn’t like to run without the outside vent assembly (gets too much air).
    Parts are still available at the RV Dealership website, among other places.

    — Chris

    Comment by Chris — December 31, 2015 @ 1:24 pm

  485. Hello,

    I have a Suburban p-40 heater (about 15 years old).

    The unit was not igniting on a regular basis. I changed the following:
    1. Thermostat
    2. Control Board
    3. High Limit Switch

    Now the unit lights and heats the room, then the fan continues to run forever until the thermostat is turned down to the off setting.

    Any ideas what might cause this? (Defective sail switch or fan relay timer?)

    Thanks! ben

    Comment by ben — January 7, 2016 @ 7:54 pm

  486. Hi Ben,
    The only 2 things that could cause that are the time delay fan relay and the thermostat. Even though the thermostat is new, I would double check it, simply because turning it off shuts the blower. If not for that, I would say the relay.
    Try testing for AC voltage on both of the (according to my diagram) white thermostat wires at the furnace after the burner shuts off but while the blower is still running. I suspect you might be getting some voltage there- just enough to keep the relay from shutting off.

    — Chris

    Comment by Chris — January 8, 2016 @ 12:54 pm

  487. Hi, we are in a 1992 skyline Layton with a Honeywell furnace, it was working fine this am then tank got low and we switched to the full tank, temp here is very cold and snowing, everything else is working on propane , fridge, and cook stove with good flame, but heater will not come on at all even tho we have checked all the wires and shut off the heater and turned it back on, we have 2 ele. heaters running now but are on a 20 amp circuit and it still won’t keep it warm in here, so we have looked at all the connections for the furnace and like I say it was fine and working well this am till we switched the tank over, we have been using the same tanks for the past 2 months and keep them full, what do you think is wrong??? We are cold and not liking this old rv for sure but it has more room than our camper and seems to be more of a pain to be in this time of the year, any suggestions would be appreciated..thanks

    Comment by Jana and Jeff — January 9, 2016 @ 8:55 pm

  488. Hi Folks,

    I’m betting you have a Honeywell thermostat, not furnace, but if nothing comes on, look at the 12 volt fuses, and there may be a 12 volt circuit breaker on the furnace itself.

    — Chris

    Comment by Chris — January 9, 2016 @ 11:27 pm

  489. I have this same problem except if I tap the housing of the furnace the blower will start and works normal thru the cycle and then not cycle again when it drops below temp setting. Would you replace the mechanical with a mercury thermostat?
    Thank You,

    Comment by Rich — January 11, 2016 @ 5:25 pm

  490. I have a brand new nt30. worked great when the installer put it in. Now it wont turn on. I played with the circuit breakers. When I turned off the breaker that runs the inverter, the furnace turned on. It comes on with straight battery power but will not turn on when plugged in and direct power?

    Comment by mike — January 18, 2016 @ 12:58 am

  491. I am changing my thermostat from a manual to digital I am having torble with the wires I can send you a pic of both I was smart enough to take a picture of the old one I need a clue thanks rolls

    Comment by rolls — January 19, 2016 @ 12:04 am

  492. I would not use a mercury thermostat in an RV- the newer electronic thermostats work very well- just find one that is battery powered, and use only the RH and W terminals.

    Comment by Chris — January 26, 2016 @ 1:55 pm

  493. That is an odd one- I would look closely at the power at the furnace- measure it with a digital meter on both DC and AC scales.

    Comment by Chris — January 26, 2016 @ 1:57 pm

  494. You can email them to me at [email protected]

    Comment by Chris — January 26, 2016 @ 1:58 pm

  495. I have a Suburban P-40 furnace, it will turn on and heatup but then shut down, anywhere from after a couple minutes to 10 minutes. The furnace is mounted in an enclosed area in a park model trailer. The furnace will try to re-ignite but goes into shut down after a few tries. The blower does not stop and after the unit cools some I can turn the thermostat down all the way then right back up and the process will repeat.
    If the furnace is removed from the cabinet and run on an open bench it will never shut down on it’s own. The module board and hi-temp switch have been changed but the problem continues. I see no obstruction in the air flow, it even happens with the front cover off. The local service shop has given up and I am getting there too.
    The problem started late in the season last year and has never gone away not even to work one time correctly.

    Comment by Tom — February 2, 2016 @ 12:41 am

  496. Hi Tom,

    That’s a tough one- does the whole unit shut down- blower and all, or does the blower keep running? Troubleshooting would be easier if you had room to install the Dinosaur Extend-a-life kit, which would let you test power to the board with the unit installed. If everything does shut down, I might suspect the transformer over heating and shutting off.

    — Chris

    Comment by Chris — February 2, 2016 @ 2:10 pm

  497. Thanks for your reply Chris.
    The blower keeps running and only stops after I turn the thermostat down and leave it down.
    I can hear the gas valve energizing and see the electrode arcing numerous times before lockout, the burner will not re-ignite until I reset the board by turning down the thermostat and then back up, which in turn resets the board. At this point the furnace will ignite again for a few minutes, then the process starts over again. I have ordered a new oriface and sail switch out of desperation, the oriface threads did seem stripped.Now with the furnace out, I have also cleaned the electrode, flame sensor and ground probe, but will wait until the parts arrive to see if any of this makes a difference.
    I am a retired machine tool and industrial maintenance electrician so I understand this circuitry, it is actually very simple compared to machines I have worked on over the years.That is why this frustrates me.
    I like your suggestion about the control transformer and when I reinstall the furnace, if I still have a problem, I will monitor the 24 volts. I can hear the gas valve energize and see the electrode arc. I wonder about that one, unless the voltage drops just enough to not fully open the gas valve. At one point, I disconnected the gas supply line from the large home tank and attached a gas supply line from a 20 pound tank. It still shut down, with doing this, I think I ruled out the regulator. Never have a problem with the pilot lights or burners of the gas stove.

    Comment by Tom — February 2, 2016 @ 10:19 pm

  498. Thanks Chris. That lady on the smart phone found you for me. It was the limit switch on a suburban furnace in an ice castle. Fishing on the ice in South Dakota in total fog at 10 o’clock at night. made a good weekend better. Thank you. My wife thanks you even more.

    Comment by Marti Keating — February 6, 2016 @ 4:21 am

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