I have a 2018 class A gas unit with an Atwood afm series furnace. My problem is that it was sooting up and smelling, even to the point of sounding off the CO alarm. I thought I had a dirt dauber problem maybe so I took the unit completely apart and flushed the heat tubes. I was wrong and that is not the issue. Ran a snake from stem to stern through it and got nothing at all. Flushed it with water also and got nothing but good flow. Here where my plot thickens. Not only have I not found the original problem, but now have another one. After putting it all back together, I now have a problem with nothing at all happening when turning the heater on. I checked the wiring diagram and see not issue, however it is possible that I am overlooking something. When we first put it back together I got a single flash light on the circuit board which pointed to the limit switch. Now though, after swapping out a couple of wires that were put in the wrong place initially, I get nothing. Any ideas? Could the limit switch getting wet during the flush, could it be stuck open not allowing the circuit to be complete upon startup. ALSO, could someone send a picture of their circuit board just to make sure the wiring is correct?

Did you verify with a meter that you have a good 12 V going to the board.Also with the meter you can ohm out the switches to see if they are working properly.Did you take a picture of the board or make a diagram of the board connections before you took it apart?

Here is manual that should help.ManualI would blow the furnace compartment out good with compressed air, compressor or can will work.Have you tested the thermostat? At furnace connect the two blue wires on terminal block. Furnace fan should start immediately. In 15-20 seconds burner should kick in. separating the two blue wires the furnace should go into cool down mode and then shut off.If no operation, Check the circuit breaker to insure it is energized. This is mounted on motor housing.

I sure wish now I had taken pictures but didn't. I do have 12 volts at the board. I didn't know if it would hurt to jump the circuit breaker, sail switch and the limit switch, not at the same time but one at a time? I will test the thermostat like one of you said next. Thanks again.

It would not hurt to jumper circuit breaker for testing only! You could take test with voltmeter. One lead to ground, other lead to each side of breaker terminals. You should have 12 volts one each side.

I,d STOP right now. your not sure of the wiring. you could damage other things by just flipping wires.

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VilleDeal
Explorer II
Jan 22, 2020
I am going to go look at it today. My rig is not parked nearby so I have to go a ways to get to it. I do have the wiring diagram in my owner's book. I am relatively sure now the wiring is correct. I will start by tying the two blue wires of the thermostat to make sure it is not the problem with it now doing nothing at all when the heat switch is turned on at the thermostat.
opnspaces
Navigator II
Jan 22, 2020
enblethen wrote:
Here is manual that should help.Manual
I would blow the furnace compartment out good with compressed air, compressor or can will work.
Have you tested the thermostat? At furnace connect the two blue wires on terminal block. Furnace fan should start immediately. In 15-20 seconds burner should kick in. separating the two blue wires the furnace should go into cool down mode and then shut off.
If no operation, Check the circuit breaker to insure it is energized. This is mounted on motor housing.

Have you figured it out yet? The manual that enblethen linked has a wiring diagram.
midnightsadie
Explorer II
Jan 22, 2020
I,d STOP right now. your not sure of the wiring. you could damage other things by just flipping wires.
enblethen
Nomad
Jan 21, 2020
It would not hurt to jumper circuit breaker for testing only! You could take test with voltmeter. One lead to ground, other lead to each side of breaker terminals. You should have 12 volts one each side.
VilleDeal
Explorer II
Jan 21, 2020
I sure wish now I had taken pictures but didn't. I do have 12 volts at the board. I didn't know if it would hurt to jump the circuit breaker, sail switch and the limit switch, not at the same time but one at a time? I will test the thermostat like one of you said next.
Thanks again.
enblethen
Nomad
Jan 21, 2020
Here is manual that should help.Manual
I would blow the furnace compartment out good with compressed air, compressor or can will work.
Have you tested the thermostat? At furnace connect the two blue wires on terminal block. Furnace fan should start immediately. In 15-20 seconds burner should kick in. separating the two blue wires the furnace should go into cool down mode and then shut off.
If no operation, Check the circuit breaker to insure it is energized. This is mounted on motor housing.
Flute_Man
Explorer
Jan 21, 2020
Did you verify with a meter that you have a good 12 V going to the board.
Also with the meter you can ohm out the switches to see if they are working properly.
Did you take a picture of the board or make a diagram of the board connections before you took it apart?

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