Forum Discussion

gedstrom's avatar
gedstrom
Explorer
Nov 30, 2013

Furnace Won't Stay Lit

I am having a problem with the furnace in my 2005 Fleetwood Jamboree. In colder weather, you can hear the burner light for a few seconds and then go back out. After a few more seconds, it repeats the process. After a third try, it shuts down and I need to reset it at the thermostat. I have taken it in for service a couple times, but they have been unable to find anything wrong of course. It probably doesn't act up for them because it has not been cold enough.

I figure that there has to be some sort of flame sensor that detects if the burner has turned on and shuts down the propane if it doesn't sense a flame within a certain amount of time. Does anyone know what this sensor would be called? They didn't seem to know what I was talking about at Camping World.

If I can identify the part, I can tell them to replace it even if it tests good. I have already wasted a couple of diagnostic expenses with them. The furnace is an Atwood 8500-IV series. I have looked through the parts diagram and can't seem to identify the part I am interested in.

Any help would be appreciated...Gary
Class C
  • enblethen's avatar
    enblethen
    Nomad
    Dec 01, 2013
    Look at your water heater circuit board. It may use the same one as the furnace. If so switch them and see if problems goes away. If you still have problem, then it is not the circuit board.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Dec 01, 2013
    The spark electrode IS the flame sensor.
    When the main flame ignites a milivolt signal is sent back thru spark electrode and wire to control board 'proving' main flame which allows power to gas valve to stay energized.

    If spark electrode is dirty or not positioned directly in main flame then signal will not go back to control board.

    If signal is being sent then problem is with control board. Unplug connector on board..clean contact are with a pencil eraser and make sure it is making good contact when you plug it back in.

    Other possibilities:
    Blocked exhaust port....clean
    Low gas pressure...should be 11" WC with at least 50% of other gas appliances in service
    Defective high tension lead from spark electrode to control board
  • Bird_Freak's avatar
    Bird_Freak
    Explorer II
    Dec 01, 2013
    Check the light on your control board and see if it flashes. If so how many times?
  • gedstrom's avatar
    gedstrom
    Explorer
    Dec 01, 2013
    Thanks for the tips. I guess this is a problem I am going to have to try to tackle myself. I just don't trust Camping World anymore. I found the "electrode" and related parts on my parts diagram. I might try to work on the thing tomorrow. I park the RV 55 miles away up in Palmdale because of the much lower parking rates, but it makes things kind of inconvenient at times.

    In regard to the blower, it seems to be working just fine. It comes on several seconds before this whole 3-try sequence gets underway and doesn't shut down until the very end. Thanks for the idea on maybe it getting too much cold air for the flame. I will look at that.
  • Bird_Freak's avatar
    Bird_Freak
    Explorer II
    Nov 30, 2013
    My 8500 did the exact same thing. Turned out to be the control board.
  • SDcampowneroper's avatar
    SDcampowneroper
    Explorer
    Nov 30, 2013
    After 4 winters of trouble like yours, numerous service in & outs by supposed pros, I realized that when the furnace lights, the flame is noisy. In other words getting too much air which blows the flame off of the burner.
    So I slowly restricted the cold air intake with electrical tape until the flame was quiet and clean. Furnace works perfectly since, does not wake us up with try try again.
    Just like adjusting the water heater burner with the slide tube.
  • enblethen's avatar
    enblethen
    Nomad
    Nov 30, 2013
    Part 18 in the schematic should be the combination ignitor electrode and flame sensor.
  • Ex-Tech's avatar
    Ex-Tech
    Explorer
    Nov 30, 2013
    Your description tells me that the ignition board is a "Thee-Try" type that after the third try, goes into lock-out.

    I suspect that the flame sensor isn't proving the presence of a flame either because of a loose connection or defective board.
    The sensor can be removed and cleaned with emery paper (not sand paper) and that could help. Also check connections on the ignition board.
  • trop-a-cal's avatar
    trop-a-cal
    Explorer
    Nov 30, 2013
    Does the fan kick on after it lights? If not that may be why it shuts off. Make sure it is unobstructed to the outdoors as sometimes people place things over the exhaust port.

About Motorhome Group

38,705 PostsLatest Activity: Jan 24, 2025