Furnace troubleshooting

[Donna D.]

Originally Posted by tom&pam

When I talked with Dometic, they would not give me any troubleshooting hints, but they did send me the service manual. That manual might help some other owners. I was going to upload the manual, but it is too big for the forum. Is there a workaround for uploading bigger files?

Can you divide into Part 1 and Part 2 rather than one big file?

[Camp@Home]

Ours quit last August after 2 mos ownership and only couple 3-day trips. Boxer hair in the sail switch! Pretty sensitive. Worked after cleaning out since. This winter I followed a post's advice and put in the solid duct and wedged filter material (cut 8.25"x12.5" piece w/5" hole from cheap $1.30 16"x20" furnace filter - made 2 so have spare) under the surrounding face plate - re: furnace intake - to keep Boxer hairs OUT! And anything else. Hopefully that should last a while. Most have indicated this is biggest issue with that and (fairly) simple fix.

[Centex]

Originally Posted by Donna D.

Can you divide into Part 1 and Part 2 rather than one big file?

I've just placed a 2018 version of the Dometic DF Series (and others) Furnace Service Manual in the moderator que pending approval for the Files>Manuals section of the forum (~7.3MB pdf).

Originally Posted by tom&pam

When I talked with Dometic, they would not give me any troubleshooting hints, but they did send me the service manual. That manual might help some other owners. I was going to upload the manual, but it is too big for the forum. Is there a workaround for uploading bigger files?

If you've got something more current than 2018 you can likely upload it here to the Files>Manuals section of the forum

https://www.escapeforum.org/forums/downloads.php

click "Add" under "Navigation"

[EscapeBoulder]

Originally Posted by davidmurphy02

The current furnace installed over the last several years is the Dometic DFSAD12131. Older models may have an A rather than a D for the first letter, indicating that they were made when Atwood was still a separate company before being bought and consolidated into Dometic. If your furnace is older the model number and serial number should be on a tag on the blower motor housing or possibly another location depending on the model. The photo below explains what the various letters and numbers in the model number mean and will tell you about the specifications of your furnace.

In my research I came across an Atwood Furnace Training Manual designed to help service techs diagnose and repair furnaces. It's long as it includes several different models of furnace, but it has a wealth of information about exactly how the furnace works, troubleshooting, parts diagrams, etc. http://techsupport.pdxrvwholesale.co...anual-2015.pdf

Thank you for the link to the furnace's service training manual. Information like that is invaluable!

[EscapeBoulder]

This is an interesting conundrum with our 2018 Dometic DFSA12-131 furnace.

It appears that it doesn’t have any power. But here’s the whole story before we assume that…

Last fall, at just below freezing, on a weeklong trip the first night the furnace worked fine. The second night it wouldn’t come on. No fan. Nothing. It was inert. So I figured this probably wasn’t an issue with the sail switch.

Upon returning home, I couldn’t figure out what the problem was, so traded out both the Dometic capacitive thermostat and the furnace’s board, of course first checking and actually trading out the furnace’s 12v fuse at the fuse box. Nothing helped.

By the time I did all that it was late enough in the year that it was time to put the trailer into winter hibernation. Done.

After taking the furnace out of winter hibernation a few days ago, the furnace was still unresponsive, so when I took the trailer into have the bearings and brakes maintained, I also asked the RV shop in Denver to fix the furnace. Upon picking up the trailer they said the furnace worked fine. No problem. And sure enough when I fired up the furnace in their parking lot, it worked. Fine.

Upon returning home the furnace worked for maybe five minutes, then went off again. And since that time remains dead.

Today I again check the thermostat (fine), the fuse (fine), and even decided just because I could, traded out the sail switch. Nothing helped.

Looking at the furnace’s board, I found the red wire connected to a connector marked “PWR” on the board and also an obvious ground. I exercised both of these wire’s connectors.

Later: With the thermostat’s furnace setting 85 degs (it was 60 degs today), I find no voltage on the red “PWR” wire.

I guess the next step could be with the thermostat set at 85, I could run a temporary separate 12v line to the board’s “PWR” connector, to see if there’s an open circuit there between “PWR” and somewhere upstream. But even if there is, due to the fact that the air conditioner and furnace are on the same thermostat, I’m wondering a) if the furnace’s board is looking for 12v on its “PWR” connector (or some other voltage), b) if putting 12v on the “PWR” connector awakens the furnace, then is that red wire coming from the fuse box, or the air conditioner or thermostat? I guess my question is: Where would I go from there.

Thank you in advance for any suggestions or advice you might have.

[John in Santa Cruz]

Originally Posted by EscapeBoulder

This is an interesting conundrum with our 2018 Dometic DFSA12-131 furnace....

Looking at the furnace’s board, I found the red wire connected to a connector marked “PWR” on the board and also an obvious ground. I exercised both of these wire’s connectors.

Later: With the thermostat’s furnace setting 85 degs (it was 60 degs today), I find no voltage on the red “PWR” wire.

I guess the next step could be with the thermostat set at 85, I could run a temporary separate 12v line to the board’s “PWR” connector, to see if there’s an open circuit there between “PWR” and somewhere upstream. But even if there is, due to the fact that the air conditioner and furnace are on the same thermostat, I’m wondering a) if the furnace’s board is looking for 12v on its “PWR” connector (or some other voltage), b) if putting 12v on the “PWR” connector awakens the furnace, then is that red wire coming from the fuse box, or the air conditioner or thermostat? I guess my question is: Where would I go from there.

Thank you in advance for any suggestions or advice you might have.

the power for the furnace should be coming form the fuse board. it has nothing to do with the air conditioner, and the thermostat is strictly a low voltage/low current control circuit

this wiring diagram is from a Dometic installation manual for the whole series of DF furnaces...

[MVA]

Originally Posted by John in Santa Cruz

the power for the furnace should be coming form the fuse board. it has nothing to do with the air conditioner, and the thermostat is strictly a low voltage/low current control circuit

this wiring diagram is from a Dometic installation manual for the whole series of DF furnaces...

John - should this also be the same wiring schematic for the Atwood furnaces?

thanks

[EscapeBoulder]

Thank you John for the schematic. It's very helpful.

Since the "PWR" connector on the board isn't getting any power, yet the fuse appears to be fine, I guess the next place to look would be at the "On/Off Switch-Breaker". Investigate if it's getting a signal from the thermostat and/or if there's power coming into it from the fuse side.

Might you know where to look for said "On/Off Switch-Breaker"?

Thank you again for the schematic!

[Ooshkaboo]

Originally Posted by EscapeBoulder

Thank you John for the schematic. It's very helpful.

Since the "PWR" connector on the board isn't getting any power, yet the fuse appears to be fine, I guess the next place to look would be at the "On/Off Switch-Breaker". Investigate if it's getting a signal from the thermostat and/or if there's power coming into it from the fuse side.

Might you know where to look for said "On/Off Switch-Breaker"?

Thank you again for the schematic!

I’ve no experience troubleshooting a RV furnace, other than a sail switch, but plenty on home units.
Maybe you’ve already tried this but using a small jumper wire, made from the same type of wire that feeds from the thermostat to the furnace connection, you can troubleshoot all things thermostat related.
Lookup using a jumper wire to troubleshoot a furnace and you’ll find plenty of helpful videos.
Spot one on the thermostat, spot two on the furnace, where the thermostat wires are connected to the furnace.
It may not be the problem you’re having but it will help to narrow down your search.

[EscapeBoulder]

Jumper wires. Good ideas. Thank you, I'll give it a try.

[rubicon327]

Originally Posted by MVA

John - should this also be the same wiring schematic for the Atwood furnaces?

thanks

Original Atwood 8012-II furnaces (early Escapes) (schematic page 4):
http://techsupport.pdxrvwholesale.co...ion-Manual.pdf

Atwood AFSAD12 furnaces (schematic on page 7):
https://pantherrvproducts.com/conten...K%20Manual.pdf

Dometic DFSAD12 furnaces (schematics Fig. 1 & 2 page 23)
https://www.dometic.com/assets/14/52...1_01_81452.pdf

Dometic bought Atwood so the AFSAD12 and DFSAD12 furnaces are similar. There have been minor design changes to the furnaces but the functionality is the same so the schematics are similar if not identical.

[MVA]

Thanks - I have downloaded the Atwood manual.

[ThomasC]

I had an intermittent problem and this thread helped me out. I had a problem built in from the factory that didn't become apparent until I pulled the gas valve out. The ignitor was touching the combustion chamber, and you will only see this if you remove them together.

Anyway there is a thread of the nightmare over on Fiberglass RVs. It may help someone out.

https://www.fiberglassrv.com/forums/...lem-97448.html