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Open Roads Forum  >  Class A Motorhomes  >  Maintenance Issues & Tips

 > Do You Have An Atwood Furnace That Won't Light?

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F4Jock

Sweet Valley, PA

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Posted: 09/19/18 07:02am Link  |  Quote  |  Print  |  Notify Moderator

So did I. Everything seemed to be working fine in my 8535 -lll. Had a propane smell, blower worked, thermostat worked, just didn't want to light reliably or stay lit. Atwood/ Dometic was no help. Told me to look at the sail switch which I KNEW had to be working or the gas solenoid wouldn't actuate.

WARNING: DO NOT TRY THE FOLLOWING UNLESS YOU ARE COMFORTABLE WORKING WITH HIGH VOLTAGE AND LPG. I TAKE NO RESPONSIBILITY FOR ANY INJURY OR DAMAGE THAT MAY OCCUR! Before doing ANYTHING get yourself a furnace schematic and a furnace blow up diagram so you know what goes where.

I took out the igniter. Some fun. First you have to remove the exhaust which just pulls out after some persuasion. Then, shut off the LPG at the tank, disconnect the ignition wire and solenoid wire at the ingiter. Four screws and the gas fitting later you can persuade the burner to come out.

Now for the good part. Measure the space between electrodes. It should be about a quarter of an inch. Mine was an eighth. Gently bend the electrodes apart or together until you get about a quarter of an inch spacing. To test, hook the ignighter and gas solenoid wires back up to the igniter. Hang the igniter assembly from the door with the electrodes facing up. Fire the heater as you normally would. After the appropriate delays you SHOULD get a visable, repetitive, rapidly snapping spark between the electrodes for about five seconds. If you get no or a weak spark the problem could be the board or electrodes. Mine originally tested very weak and did not repeat, but when I opened the electrode gap to one quarter of an inch the difference was dramatic.

Reassemble and test. I highly recommend using SNOOP or some other leak detector at the propane fitting after you have reattached it. A leak could be deadly! Remember that the propane line will be empty so it will take a few tries to ignite. After all of this my furnace now lights and runs flawlessly.

Once again, this procedure is NOT for someone who does not know how to work around flammable gasses and / or high voltage. You could be killed, or even worse! You have been warned!


Patti, Jack, our GSD Gunner the Wonder Dog and our multtude of cats.
1998 National Tropi-Cal on a 1997 Ford F53 chassis with 460 Ford power.

dobbler98

Ohio

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Joined: 05/01/2005

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Posted: 03/13/19 01:41pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks for this post. I"ve had mine apart 3 times which is a headache in itself. Replaced the ignition board, sail switch, high limit switch, and cleaned it thoroughly. Still no ignition...proving that there was nothing wrong with the board to begin with, Grrr. Anyway, based on your post, I'm gonna let somebody else struggle with the burner assembly.
Thanks for saving me more headaches cos I'm not comfortable doing what you did.
Happy Trails


2004 Holiday Rambler Admiral SE 30PDD
Usually pulling one of my toys ">


Dutch_12078

Winters south, summers north

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Posted: 03/13/19 03:10pm Link  |  Quote  |  Print  |  Notify Moderator

The electrode spacing according to Atwood should be 1/8".

Atwood Furnace Service Manual (Page 25)

Also, never try to bend the electrode with the porcelain insulator, it will crack. Always adjust using the ground electrode.


Dutch
2001 GBM Landau 34' Class A
F53 chassis, Triton V10, TST TPMS
Bigfoot Automatic Leveling System
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox baseplate


wa8yxm

Wherever I happen to park

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Posted: 03/13/19 03:52pm Link  |  Quote  |  Print  |  Notify Moderator

To answer the question.. No, then yes. then no now sometimes.

We will skip the first NO.
Then it would actually light off. but only for a few seconds. then it would try again and again then it would lock out.. I tested everythign I could.. Thermocouple put out the proper voltage.. Flame was good... Decided the chip on the mother board that detects the 0.480 volts got zapped.

Put in a Dinosaur board. 100% functional.. NOTE Dino board was half the price of Atwood. and way way way way better built. also I think I know what happened to the Atwood board. Looks like Dino thinks the same cause they put a protection device on their board that the Atwood did NOT have.


Then it stoped even trying. blower would not come on.. I'm still working on that but it appears to be a short in the blower motor leads. Sometime it works. and I can make it work when I have to if I am parked.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377


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