LP furnace fan won’t turn on, furnace will not ignite

[Marvelous]

Disclaimer: yes, I am a AS newbie 2018 23D International : )
Summary issue: I cannot get my LP Atwood furnace burners to fire.
“Upstream” issues:
1. LP furnace fan won’t turn on, so sail switch will not permit furnace to ignite
2. Dometik thermostat modes on include “OFF”, “COOL”, “HP”, and “AUTO”. “FURN” or “AQUA” does not show up in the mode menu.

Things I have checked:
1. Propane is turned on. HW heater is working and stove top ignites immediately.
2. No breakers are tripped and all fuses in the primary panel below the fridge are good.

Questions:
1. Why doesn’t Dometik thermostat mode menu include FURN as an option?
2. Is there a remote gas supply valve to the Atwood furnace somewhere?
3. Is there a remote fuse or breaker for power to the furnace not in the primary panel below the fridge?
4. What question should I be asking?

Answers:
... so far I have not come up with any answers; looking for your help.

Thanks, Marvelous in New Mexico

[GCinSC2]

Furnace model number?

[Marvelous]

Atwood model number is AFMD26141

Also, just in case someone asks, there is not a flashing LED indicating Ignition Control Diagnostic error.

Not so Marvelous

[GCinSC2]

This might help an Atwood service manual that includes the AFM series.

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

Darren at My RV Works Youtube also has multiple furnace videos.

[Marvelous]

GCinSC2, the links you provided were very informative, especially the Atwood installation manuals. With a voltmeter, I was able to confirm I have 12vdc power going to the Atwood furnace but the Dometic CCC2 thermostat does not show a FURN option when I cycle through the mode options. My suspicion is that the furnace option on the DIP switch is not switched on. When it warms up outside, I will go search for the control box in the AC unit and see if I can find that DIP switch. Thanks again, Marvin in NM

[AzAirstream]

There is a procedure to reset your thermostat. I would try that. I think the process is listed in your manuals. Good luck.

[Rich W]

My AS is in storage so I'm just going to take a stab in the dark. I recall there are settings for Zone 1 and Zone 2. It being a 23' I'd make sure that it was set for Zone 1.
HP is heat pump but no idea what AQUA is. I think ours just says HEAT as an option.
Does your fan come on? Ours has a setting for Fan Only.

[D-Rod]

Go on u-tube and see how to service the sail switch in the blower motor to the furnace. It’s a safety feature designed to blow out excess fumes upon start up. If it’s become dusty it will prevent the switch from making contact to run the blower thus sending a signal not to light the furnace. It’s a really quick and easy fix.

[CruizinDux]

Originally Posted by AzAirstream

There is a procedure to reset your thermostat. I would try that. I think the process is listed in your manuals. Good luck.

I agree, hard boot of stat often solves many issues.

[GCinSC2]

Originally Posted by Marvelous

1. LP furnace fan won’t turn on, so sail switch will not permit furnace to ignite

Thanks, Marvelous in New Mexico

Originally Posted by D-Rod

Go on u-tube and see how to service the sail switch in the blower motor to the furnace. It’s a safety feature designed to blow out excess fumes upon start up. If it’s become dusty it will prevent the switch from making contact to run the blower thus sending a signal not to light the furnace. It’s a really quick and easy fix.

D-Rod,

See post 1, line 1.

Furnace fan has to turn before the sail switch comes into play. That is part of the sequence of events to fire the furnace.

Gary

[GCinSC2]

Originally Posted by Marvelous

GCinSC2, the links you provided were very informative, especially the Atwood installation manuals. With a voltmeter, I was able to confirm I have 12vdc power going to the Atwood furnace but the Dometic CCC2 thermostat does not show a FURN option when I cycle through the mode options. My suspicion is that the furnace option on the DIP switch is not switched on. When it warms up outside, I will go search for the control box in the AC unit and see if I can find that DIP switch. Thanks again, Marvin in NM

Marvin,

That factory service manual info is courtesy of docs complied by Darren at My RV Works. Go to his website and select resources and you can search by product and manufacturer. He is a mobile RV tech in Washington State. But his website and Youtube channel have lots of helpful tips and info. https://www.youtube.com/channel/UCoK...ZLCD3flLXZVQvw

Good luck,

Gary

[guskmg]

If you have propane and electrical to the heater check the following: take off the heater front cover and cycle the on/off master switch inside the heater making sure the thermo is on and furnace is selected. Wiggle all the wires inside the furnace. If the blower comes on even for just a minute you have a bad connection. Re-splice/re-connect as necessary. If your furnace has any three way splices they are in suspect. Also, I would pull the board and clean all those contacts. If none of the above work you probably have a bad board or dip switches.
guskmg

[Marvelous]

After reading the Dometic CCC2 installation manual, I came to suspect (and hope) the FURN DIP switch on the DIP switch unit in the AC electronic control box had not been set to ON. After disconnecting all power (important) and getting up on top of the AS, removing the AC cover, removing the electronic control box cover, I was ‘relieved’ to find the FURN DIP switch set to OFF. I set it to ON, buttoned everything back up, turned the power back on, and did a factory reset on the CCC2 thermostat. I checked out out the mode options and FURN came up as an option. I increased the temp on the the thermostat, set the mode to FURN and the fan turned on. After small delay, furnace ignited and warm air came out the ducts. SUCCESS!

[AzAirstream]

Originally Posted by Marvelous

After reading the Dometic CCC2 installation manual, I came to suspect (and hope) the FURN DIP switch on the DIP switch unit in the AC electronic control box had not been set to ON. After disconnecting all power (important) and getting up on top of the AS, removing the AC cover, removing the electronic control box cover, I was ‘relieved’ to find the FURN DIP switch set to OFF. I set it to ON, buttoned everything back up, turned the power back on, and did a factory reset on the CCC2 thermostat. I checked out out the mode options and FURN came up as an option. I increased the temp on the the thermostat, set the mode to FURN and the fan turned on. After small delay, furnace ignited and warm air came out the ducts. SUCCESS!

Great news! Is this a great forum or what! Congrats. Terry

[GCinSC2]

Marvin,

Excellent detective work. Congrats. consider monitoring the output air temp and figure a baseline and recording it somewhere. Then if you're ever wondering of it's up to snuff, take temp again and compare.

Thanks for posting a conclusion too.

Gary

[Marvelous]

Postscript: We bought this 2018 International 23D from a couple in Colorado. They originally bought it in Minnesota, and that is where the dealer set it up. When I asked the prior owners if they ever used the propane heater and told them where it was located, they said they only used the heat pump and did not know they had a propane heater ... kind of amazing.

But even more amazing was that this Airstream was purchased in Minnesota, and when it was set up in Minnesota (not to be confused with a tropical paradise), whoever set it up, never enabled the FURN DIP switch, and the owner chain before me never questioned that they did not have a FURN (propane furnace) option when they cycled through their thermostat mode options.

Well, all is well now. On to other things.

Marvin in New Mexico

[J-Dog]

Originally Posted by Marvelous

After reading the Dometic CCC2 installation manual.... SUCCESS!

Congratulations on figuring it out with a successful outcome.......I too had a recent furnace issue while de-winterizing the trailer 4 weeks ago (to take a two week trip to the Oregon coast).
I flipped on the thermostat and it would immediately blow the fuse, after the second fuse I felt it was time to troubleshoot. Didn't take long to find the squirrel cage wouldn't move more than a quarter turn before hitting an obstruction, further investigation revealed a very large clay mud dauber nest was the culprit. It took about a half hour to clear the debris but promptly fired up after removal. I was so happy it wasn't something worse. The trailer is now back in storage and those buggers won't be getting in any longer, everything has been sealed off to prevent them from entering again.