Atwood Furnace Trying To Self Start

[1L243]

I have a Atwood Furnace AFMD30111. I just returned from a 3 day trip where the furnace was used a lot. Today when cleaning the trailer I heard a noise which sounded like a small fan. I finally tracked the noise to the furnace. It sounded like a small fan motor and maybe a igniter trying to start.? The thermostat was turned OFF. I finally had to pull the 12 volt fuse from the fuse panel to get the noise to stop. Put the fuse back in and the noise returns.

Any suggestions on what this could be or how to fix it?

[1L243]

This morning after doing more research I thought I would check the sail switch for hair or bad contact. It looked fine.

When I went in the trailer I had removed the 12 volt fuse the night before because it was the only way to turn off the furnace fan. I noticed that the red LED light next to the fuse location was out. I was thinking that the red LED was on because of the removed fuse? I put the fuse back in and the furnace did not come on. I went to the thermostat and turn on the furnace, fan came on as normal, 15 seconds later furnace ignited. All seems as it should.

So, my guess is that it had overnight to dry and I caught it before it fried the circuit board?

Thanks for the Atwood contact information I will be contacting them for a Retrofit. This is a problem you don't want to have when it's 20 degrees outside.

Thanks for the help.

[Old-Biscuit]

1L243 wrote:
Found a related youtube video which explained that some Atwood models have a problem with the circuit board sitting flat on a plastic tray. Water can accumulate on the tray causing the circuit board to short out. This kind of made sense to me because I had just towed my trailer home in a major rain storm.

I pulled the cover to the furnace and removed the circuit board sure enough there was water sitting in the tray. I dried out the tray and used canned compressed air to dry the circuit board. I replaced the fuse and turned on the furnace. The fan motor would run and blow cold air but would not light. It would continue to run til I removed the fuse. So, board must be toast.

Apparently Atwood has come up with a retrofit including a new circuit board that mounts the board vertically and according to the youtuber free of charge. We will see about that. Regardless I will try and track down the Retrofit kit.

Anybody had a similar problem?

Contact Atwood (Dometic) and inquire about a 'relocation kit' so circuit board stops getting wet (Atwood 32596)
800-366-3842

*they have replaced for free out of warranty....won't hurt to call & inquire

If NOT....cheapest seen via Internet
Atwood Furnace Circuit Board Kit


OR...fabricate a 'lift' for your circuit board similar to bracket show in link???

[dougrainer]

1L243 wrote:
Found a related youtube video which explained that some Atwood models have a problem with the circuit board sitting flat on a plastic tray. Water can accumulate on the tray causing the circuit board to short out. This kind of made sense to me because I had just towed my trailer home in a major rain storm.

I pulled the cover to the furnace and removed the circuit board sure enough there was water sitting in the tray. I dried out the tray and used canned compressed air to dry the circuit board. I replaced the fuse and turned on the furnace. The fan motor would run and blow cold air but would not light. It would continue to run til I removed the fuse. So, board must be toast.

Apparently Atwood has come up with a retrofit including a new circuit board that mounts the board vertically and according to the youtuber free of charge. We will see about that. Regardless I will try and track down the Retrofit kit.

Anybody had a similar problem?

Yes, that is the problem and the kit fixes that problem. Doug

[1L243]

Found a related youtube video which explained that some Atwood models have a problem with the circuit board sitting flat on a plastic tray. Water can accumulate on the tray causing the circuit board to short out. This kind of made sense to me because I had just towed my trailer home in a major rain storm.

I pulled the cover to the furnace and removed the circuit board sure enough there was water sitting in the tray. I dried out the tray and used canned compressed air to dry the circuit board. I replaced the fuse and turned on the furnace. The fan motor would run and blow cold air but would not light. It would continue to run til I removed the fuse. So, board must be toast.

Apparently Atwood has come up with a retrofit including a new circuit board that mounts the board vertically and according to the youtuber free of charge. We will see about that. Regardless I will try and track down the Retrofit kit.

Anybody had a similar problem?

[Old-Biscuit]

Either the thermostat is shorted allowing 12VDC to signal furnace circuit board
OR
Circuit board is faulty

12VDC form Fused source goes to Furnace PWR on circuit board...12VDC + is always at the circuit board
**same DC goes to thermostat

When thermostat Closes the DC goes back to circuit board at 6 pin connector via Blue wire --- this triggers the BLW circuit to energize the FAN Motor

Another Blue wire is at that connector...it is from sail switch/limit switch circuit
This Blue wire should ONLY be hot when fan has come up to speed closing sail switch

So thermostat Has to be closed in order for DC to go back to circuit board....if OFF then it could be shorted

But with DC always at the circuit board PWR section... the circuit board could be faulty allowing DC to BLW section causing fan to run etc

Remove thermostat...disconnect either one of the Blue wires.
If Furnace stops then thermostat is shorted

If furnace continues to run...then circuit board is faulty


See Pg 8 for wiring diagram

[enblethen]

Bad thermostat
Make and model of thermostat?
Remove cover from the thermostat disconnect wire to the furnace. See what happens.