Atwood Dometic furnace manual

[jdarwin]

I’m hoping someone can direct me to a link with my furnace manual. I called Keystone and they told me I have a Dometic furnace. My model is DFMD35131. I removed the cover and got the model and s/n. However nothing shows on searching the Dometic site. Atwood has a model AFMD35131. However it is grouped in with all their other models.

The furnace blower turns on but the Unit ignites for a few seconds and stops. I checked the sail switch and it is clean, no dust bunnies. Any ideas on next steps?

Thanks

[Carl n Susan]

Here are two PDFs from the files section:


1. A generic troubleshooting guide for Atwood furnaces https://www.montanaowners.com/forums...?do=file&id=11


2. A manual for a earlier (2007) model but proably not too different from what you have https://www.montanaowners.com/forums...?do=file&id=26

[DQDick]

Part of the confusion is that Dometic now owns Atwood so it's the same company. I'm assuming you are sure you have gas and no air in the lines. I don't know what year rig you have, but on our 2017 water could get in and short the board but it really sounds like a sail switch problem. Dometic had some bad switches on our year and I'm not sure how many other years. Our problems didn't seem to be sail switch related, but once we changed it out the problems all went away.

[ChuckS]

Since you indicate the furnace is igniting then I’d be looking at the flame sensor or a hi limit sensor that’s opening up when furnace fires off... Since this is an Atwood furnace the furnace control module will have a LED on it that flashes a fault code....

I’d read the fault code and go from there

[Daryles]

I found this one

https://techsupport.pdxrvwholesale.c...ood-afmd35131/

[Daryles]

Just a quick check, swap the self resetting 15A fuse with a normal one.
The self resetting fuse is notoriously unreliable.

[jdarwin]

Thanks for the help. I have a 2019 3931fb. After checking the sail switch, the blower comes on and the furnace ignites intermittent. The furnace will come on and go off for various lengths of time. It makes me think the sail switch is bad. Any thoughts?

[Daryles]

Swap the fuse. Quick easy and eliminate that possibility.

[jdarwin]

I checked and all the fuses are normal 15amp. I have no resetting type fuses.

[ChuckS]

If you read the code on that Atwood furnace it will help you to not guess at what the issue is..

I’d be checking

[ChuckS]

I’d start at about page 45 of this service manual for your Atwood... now made by Dometic furnace issues....

https://myrvworks.com/wp-content/upl...ing-Manual.pdf

[Carl n Susan]

Great reference ChuckS! I uploaded the manual to the Files section for future ease of reference.

[ChuckS]

Great reference ChuckS! I uploaded the manual to the Files section for future ease of reference.

Thanks... I hope it helps the fella out.. and maybe others down the road.. great group of folks you have on here with many years of RV background and Montana experience....

[jdarwin]

I want to thank everyone who contributed to helping me out. I believe the problem is a defective limit switch. I checked the LED. It was not flashing. I pulled the sail switch and tested it. It was OK. I reviewed the manual. Page 44 suggests the problem is the limit switch. My next step is to replace it. I did find an interesting video on YouTube of a guy explaining the problem on a 8500 model (very similar to mine). His problem was the igniter. Since mine is only a 1 1/2 yrs old, and the unit will ignite (just not continuously) I believe it’s the limit switch. I’ll update everyone after I replace the switch.

I appreciate everyone’s help. Here’s the link to the YouTube video.
https://youtu.be/AB69oqtSiwc

[jdarwin]

From doing some research the service manual shows the limit switch behind the fan. The schematic indicates a blue wire runs between the sail and limit switch. Before I go any further I'd like feedback. Is the part circled in yellow the limit switch. I'm not the best when it comes to electricity.