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Old 12-01-2019, 12:51 PM   #1
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M.O.C. #25406
Furnace Not Working

We have a 2018 362RD that we are living full time in. In preparation for cold weather I tried running the furnace and cannot get it to run. The outer blower wonít turn on and the igniter wonít click. The furnace fan runs for about 30 seconds and shuts off. Iíve check the power from the battery to the fuse panel and the fuse panel to the circuit board. There is power to the board and reset switch but nothing else seems to have power when calling for heat from the thermostat. The red led on the circuit board wonít come on at all. It looks like I have 4 wires coming to the unit. Red, Black, and 2 blues. The blue wires go directly to the side of the blower motor and there isnít power on them when calling for power from the thermostat. Is this a circuit board issue or thermostat. The thermostat controls the rear AC, rear Heat pump, and furnace. The ac and heat pump work fine. I have full propane tanks and everything else that can run off propane works. Iím electrically challenged but can work through things. The unit is an Atwood AFMD35. Thanks
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Old 12-01-2019, 01:22 PM   #2
Carl n Susan
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M.O.C. #4831
Possible mud daubers or sail switch problem. There is an indicator LED which will help diagnose. Start wit the RV Furnace Troubleshooting manual in the Files section. http://www.montanaowners.com/forums/...?do=file&id=11
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Old 12-01-2019, 06:15 PM   #3
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Classic sail switch symptoms.
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Old 12-08-2019, 12:43 PM   #4
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M.O.C. #22087
Sail switches are a common problem and are cheap enough to have a spare or two on hand. Mine went on cold night and I replaced it with a new one. Next day I connected my multimeter to the old switch and blew it out until it would make connection reliable over many activations. Now keep it in a box until needed.
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Old 12-08-2019, 01:01 PM   #5
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M.O.C. #20949
Since the RED LED light is not coming on at all it makes me suspect of the furnace control module board...

It should light up with 1 flash every 3 seconds if sail switch isnít making continuity.

The sail switch and hi limit switch are easy to trouble shoot ... sail switch will show continuity when moved one direction and itís normal state would be OPEN with no air flow..

Hi limit switch MUST show continuity always or furnace will never ignite ....

Normal operation would be 3 complete attempts of the blower coming on with failure to ignite followed by ďlock outĒ mode from the controller if furnace light off not detected.

Use your multi meter and verify sail switch and hi limit switch are good before ordering parts...
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