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Thread: RV: Atwood Furnace won't Stay Lit

  1. #1
    Ulysses
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    Default RV: Atwood Furnace won't Stay Lit

    Hi. I have an Atwood Excalibur 8500 III hydro flame furnace. It comes on
    and the burner ignites but it won't stay lit. It "attempts" to light the
    burner several times even though it is actually lit and then it just shuts
    down the gas (propane) and the blower continues to run (until we freeze to
    death, turn it off, or the battery runs down).

    According to Atwood's web site there are many things that can cause this
    problem including low gas pressure, bad circuit board, bad flame sensor, too
    much static pressure, not enough static pressure, bad wires, loose blower
    wheel etc. I found that the blower housing had a missing screw which would
    cause low static pressure. I replaced the screw and the furnace worked
    fine--for a while. Then it started doing it's thing again.

    I have not tested the circuit board, the gas pressure, or the static
    pressure as of yet mainly because getting all of the needed equipment to do
    this would probably cost as much as a new furnace. I have checked the sail
    switch, checked the exhaust for obstructions, checked for loose connections
    etc.

    I would like to know before I yank the thing out and take it apart if there
    is a common problem with these furnaces that can cause this particular
    problem. I found an aftermarket circuit board but it costs $150 and it says
    that after two failed attempts to light the furnace it shuts down
    permanantly. Sound rather final. Also sounds like maybe you need to buy
    another $150 board if it shuts down. But at least it doesn't keep the
    blower running ;-)

    Thanks

  2. #2
    Ulysses
    Guest Ulysses's Avatar

    Default RV: Atwood Furnace won't Stay Lit

    Wow. Fast responses!

    Thanks. I did sorta clean the circuit board by brushing it gently and
    blowing it off. Sounds like it needs an extreme cleaning. Or a new one.
    I'll check the stuff you suggested.

  3. #3
    Ulysses
    Guest Ulysses's Avatar

    Default RV: Atwood Furnace won't Stay Lit

    Thanks. Those are much better prices than are in the RV Parts catalog that
    I was looking at.

  4. #4
    Max
    Guest Max's Avatar

    Default RV: Atwood Furnace won't Stay Lit

    > I'm having a little trouble finding the burner and the sensor. Do I get
    > to
    > it from the front (outside access door) or from inside where the ducts
    > come
    > out? What needs to be removed to get to it? I can't even see a flame
    > anywhere when it is running.
    >
    > Thanks.


    Do I understand that you are saying that the main burner is not coming on?
    If you can't see any flame, that would
    seem to be the case.
    You should be able to access the flame sensor from the outside. It is
    located somewhere near the spark ignitor.
    It should be situated where the main burner flame can impinge on it. If the
    sensor does NOT sense heat it closes
    the main burner valve.
    Not to be sarcastic but if you can't locate the sensor, I wouldn't advise
    trying to fix it.

    Max

  5. #5
    Ulysses
    Guest Ulysses's Avatar

    Default RV: Atwood Furnace won't Stay Lit

    Thanks. That should be very helpful. I went and stared at the thing for a
    while and finally decided where the burner had to be. I found it and my
    electrodes/sensor all looked almost brand new (1997 Skyline TT). I guess
    that leaves the circuit board...

    Thinking that it could also be a "static pressure" problem I disconnected
    one of the ducts and it was working fine. But it was also working fine for
    several runs after I removed the burner and put it back. Gotta be a bad
    board to be so intermittent...

  6. #6
    Ulysses
    Guest Ulysses's Avatar

    Default RV: Atwood Furnace won't Stay Lit

    After checking the ignitor and sensor and still having the intermittent
    problem with the furnace not detecting the flame I removed the circuit board
    and examined it under 8X. I noticed several solder joints that appeared to
    have a tiny bit of corrosion around the component leads. I also found one
    circuit that appeared to have been overloaded. I resoldered all of the
    suspect connections and jumped across the overloaded connection and
    reinstalled the board (after cleaning off the flux). So far it is working
    perfectly now (for two days). We'll see.

    "Neon John" <johngdDONTYOUDARE@..............> wrote in message
    news:eh6io0hu0u4vofbhadsdm7pmf4pksrlrvt@...........
    >
    >
    > The flame proving circuitry on the control board is rather lame (I
    > reverse-engineered mine so I could do some repairs) so it might be the
    > board. My experience is that if any conducting gunk builds up on the
    > board then the flame proving circuitry becomes erratic. Clean the board
    > with pure grain alcohol, scrubbing the solder side with an acid brush or
    > equiv and then bake it out at about 150 deg in your oven for a few hours.
    > If that makes it work then the board is marginal. I put a conformal
    > coating (Krylon krystal clear spray) on mine to resurrect it for awhile
    > but that was a temporary fix.

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