Atwood Furnace help

[kcamp99186]

Am boondacking and furnace worked Monday and started Tuesday. On Tuesday it warned up the cabin and never came ba I on. Cycling the thermostat allows the blower to start. It runs for several seconds and quits. I can hear no solenoid or ignition clicks. This furnace just has a small exhaust outlet, no door. I have a few tools, but no meter with me. Any ideas or am I stuck this trip without heat? Thanks!

[jsmith948]

Am boondacking and furnace worked Monday and started Tuesday. On Tuesday it warned up the cabin and never came ba I on. Cycling the thermostat allows the blower to start. It runs for several seconds and quits. I can hear no solenoid or ignition clicks. This furnace just has a small exhaust outlet, no door. I have a few tools, but no meter with me. Any ideas or am I stuck this trip without heat? Thanks!Just had a similar issue with our Atwood. Turned out to be a bad control board. If your trailer has an exterior access door, you can get to the sail switch and limit switch and the control board. If all you have on the outside is the exhaust port, the furnace has to come out. There is an led on the board that will flash a code.

[jsmith948]

Just had a similar issue with our Atwood. Turned out to be a bad control board. If your trailer has an exterior access door, you can get to the sail switch and limit switch and the control board. If all you have on the outside is the exhaust port, the furnace has to come out. There is an led on the board that will flash a code.Check your battery charge. If the voltage is too low, the furnace will malfunction.

[kcamp99186]

Think it's the sail switch. Messed with it some and while the furnace was sitting on the floor it went clear through the cycle to solenoid open and ignition clicking was heard. Put back in place and didn't work. Quit just as before. Had my son bring me a new switch today and again it worked on the floor but not in place. Wondered if air in the propane line is the issue now. Bled the line and am waiting for air to clear before trying again.

[CampNBrew2]

"On the floor"? Does that mean you pulled the furnace? I wonder if possibly the sail switch was doing its job and the airflow could be blocked once installed? Another troubleshooting step but good to make sure air is flowing.

[kcamp99186]

Yes, by on the floor did mean I had to pull it. My furnace doesn't have the outside door. Not sure what could be impeding the air flow but we did pull a couple of the 4 ducts off and it still failed. Thanks!

[jsb5717]

I had that happen in an older 5er so not sure if this will help. On mine, I could access the control board via the exterior panel. I removed the board to get it tested. It was fine. I reinstalled it and it worked perfectly. I realized that just the process of removing and reinstalling the attached wires, which are more of a slip-on plug, that the connection was reestablished.

If that is similar to what you have, then just jiggle the wires a bit (making sure the plugs have good contact with the board) and see if it works. That's the advise I gave my father-in-law when his stopped working and it solved it for him as well. Good luck.

[Irish1955]

a coup;e years back my furnace acted similar. I found the high limit switch was bad.. replaced and it has worked well since..

[kcamp99186]

Got home last night. Good suggestions. I will try reconnecting the wires and check the limit switch today. Thanks so much.

[kcamp99186]

Thanks to you all. It ended up being a simple loose connection. Pulled all connections, then reconnected them and everything worked.

[bikegeek]

I'm having the same issue as well on a new 2018 Impact.

A couple weeks ago, we took the coach to a local powered campsite at an elevation of around 6000 ft (this detail will be important later) to de-winterize and prep for an upcoming trip. The furnace worked until the middle of the night and we woke to a very cold coach. The next day a mobile tech and I pulled the furnace and he bench tested it and everything worked on the bench, but he noticed that some wires were a bit loose, so he tightened everything up and we reinstalled and it worked ... for a day or 2.

We left town 2 days later, got to our boondocking site at about 9000 ft, and the furnace didn't work. The batteries showed full power and we just filled both propane tanks and they both were heavy. I shut the coach master power off then back on and the furnace then worked and cycled on and off appropriately for about an hour, then quit with the same symptoms. We tried power cycling the unit, as well as the entire electrical system several times again to no avail. The stove and fridge lit and worked fine. Multiple times during the trip we tried the furnace 3 or 4 times - power cycling the furnace between each attempt with no success.

I called a couple mobile techs where we were, and one mentioned that it could be a sail switch or the board. Another tech mentioned that this was common with the newer Atwoods because of the altitude. He said these units were made for lower elevations and that going up caused them to fail because they need some type of aftermarket baffle installed. I guess the propane-air mix is off. Our stove always worked - no apparent air bubbles in the line. The fridge did have a little trouble lighting up once during this stay, but i just swapped tanks then back again and everything worked.

She's going in to a warranty approved service center next week for this, but this looks like it could turn into a situation where it works at the shop and won't work out in the field, so I'd like to provide the techs with some things to check and try so we can get this fixed once and for all.

I'm thinking they need to pressure test the whole propane system, as well as the specific branch for the furnace. Is this a thing?

I'd like to see them just replace the board as that could still be it.

I'd also like them to install this baffle. Has anybody heard of this and can explain - is it not enough O2 - and how would a baffle which limits airflow correct this? Where would this baffle be placed - on the intake at the vent port on the external side of the coach, or in the furnace near the sail switch?

Any other thoughts on what to test or what could be the problem?

Thanks!!

[jefisch]

Did anyone find a resolution? I'm having the same issue where the furnace fails to light when installed, but works fine on the bench. It's still on warranty, so I took it in for service, but they could not find a problem with the furnace, nor with the inputs from the coach.

2018 Passport 2510RB with an Atwood/Dometic AFMD30121 furnace.

[CampNBrew2]

My first thought is the airflow switch may not be made up. If it works on the bench it should work in the trailer.
Fuel pressure/supply OK?
12v and thermostat signal?
If so its a safety in the heater holding it off.

[jefisch]

I just spoke to Dometic Customer Service. They recommended installing their 'High-Altitude' Vent kit for use above 5000 feet. Might be worth a try, but I'm skeptical. My furnace worked at 5600' on Tuesday. On Wednesday it did not work and I had not moved an inch. FWIW

[flybouy]

I just spoke to Dometic Customer Service. They recommended installing their 'High-Altitude' Vent kit for use above 5000 feet. Might be worth a try, but I'm skeptical. My furnace worked at 5600' on Tuesday. On Wednesday it did not work and I had not moved an inch. FWIW

The altitude kits are to compensate for lower oxygen content at altitude. If you have a significant shift in barometric pressure then it can alter the "effect" of either a lower or higher altitude.

[kcamp99186]

Mine turned out to be loose connections on the control board. I unplugged them one at a time and reconnected them. Worked fine after that.

[kcamp99186]

Hello all. Reposting in this thread that I started last year when I had a furnace (wouldn't ignite) issue. Thanks to all of you on this forum for helpful advice! As stated, I thought my problem was solved by removing and reconnecting the wires on the control board. This did indeed cause the furnace to run properly, and I had briefly run the furnace on 2 other occasions to recheck that it did still ignite and run.

Went on a weekend fishing trip this weekend and the furnace started and worked on Friday evening. Stopped sometime in the night. Pulled it out on Saturday afternoon (after fishing) and reseated the control board wires and still nothing. The LED on the board it indicated an issue with the air flow or limit switch. Checked both (sail switch checked with fan running) and they are good. But then after putting it all back together, it ran again!? For over 40 minutes it ran fine. Left to go fishing, turned thermostat down to 65, and returned to a cold camper with no working furnace. Packed up and returned home.

I'm thinking maybe a new control board, a new furnace or something along those lines. My dad, a retired electrician, started me thinking about the battery. I have the original battery from 2015. I have a Battery Tender mounted in a plastic enclosure on the front frame, permanently connected to the battery, that I plug in when in storage. Now I'm wondering if a weak or worn out battery could be the issue? I've reread this thread and see that someone did mention this before, but after I had it working again I thought no more about it. Shame on me!

I will be doing more investigating and will post any follow up results to share. So thankful for the folks on this forum.

Ken

[sourdough]

I'm thinking control board. They can do some really sneaky, intermittent things. Also, when my Dometic thermostat (capacitive touch) went bad it started doing stuff on its own as well.

[kcamp99186]

Thanks for the reply. I'm not sure what brand thermostat I have, but Ill check that as well. I believe I'll be replacing both the battery and the board. Need to pull the furnace again to find the model and see which board I need.

[LHaven]

I have a Battery Tender mounted in a plastic enclosure on the front frame, permanently connected to the battery, that I plug in when in storage. Now I'm wondering if a weak or worn out battery could be the issue?

I wouldn't feel safe assuming that a battery tender wasn't acting as a vampire load on your battery when it wasn't plugged in. I'd throw an ammeter in that loop while everything else is unpowered, just to reassure yourself.

[chuckster57]

I wouldn't feel safe assuming that a battery tender wasn't acting as a vampire load on your battery when it wasn't plugged in. I'd throw an ammeter in that loop while everything else is unpowered, just to reassure yourself.


I have to agree. An amp gauge would tell the real story.

[kcamp99186]

Thanks to you both! I will check and post my findings.

[Aireman]

I know this sounds caveman, but when I had a mobile tech come check mine for the “ fan runs and turns off without ignition “ problem , he pounded on the top of the unit in the fan just starting cycle. It kicked on and he knew to change out the sail switch. He used the Atwood warranty and charged me just $45 bucks.

[66joej]

Yep that's how the Tech did the troubleshooting on mine. Same problem same fix.

[plgamble]

I am having the same problems with my DFMD35-121 furnace, in a 2018 Outback 210 urs. Fan comes on, no ignition. I have learned the circuit boards are suspect, and fail often. If you go in for warranty work, you will get the same OEM board. Insist on the Dinosaur brand, or call them at 541-994 4344, and provide your model number for the correct board. I don't have an outside door, so I am ordering the sail switch and limit switch from Amazon, and the board from Dinosaur, just in case. But given the reputation of the OEM boards, and the difficulty of furnace removal, I'm putting the board in no matter what, and will carry the OEM as a spare.

While I'm waiting on parts, does anyone with same or similar model know about how much slack is in the wires, and how to rig up temporary propane supply for bench testing?

Thanks for any input!

Phil

[66joej]

While I'm waiting on parts, does anyone with same or similar model know about how much slack is in the wires, and how to rig up temporary propane supply for bench testing?

Thanks for any input!

Phil

No slack in the wiring harness. Have to be cut and use butt connectors to reattach the harness.

[chuckster57]

No slack in the wiring harness. Have to be cut and use butt connectors to reattach the harness.


That’s about typical for any furnace in any trailer.

[Roscommon48]

just to many variables....get to a repair shop. it could just be your LP reg. or low tanks too.

[plgamble]

Thanks for the pointer on the regulator. During our last trip, I was getting squirrelly propane readings on the regulator gauge, even when the tanks felt full. I have ordered a mechanical propane scale, and, a screw on adapter gauge.

The stove works fine, and the fridge ran on propane ok while boondocking and travelling, could there be a gas pressure problem with the regulator that affects the furnace only? Thanks to all for your help!

Phil

[sourdough]

When this last regulator failed (2-3 months ago) it did affect the furnace. The stove would burn but if I turned on all 3 burners and let them go they were at a reduced flame from normal. As it got worse they would come on and eventually die. I figured the furnace tried to pull more LP than the regulator would allow. New reg and all was good.

[kcamp99186]

I have checked my sail switch, closes every time. Actually changed it last year when the issue began, but have kept the old one as backup because it was good. Never considered the regulator. I've experienced propane issues before and am now wondering if that may be part of the problem. I'll try the "burner test". I'm awaiting a new board and my furnace currently resides in my garage until it comes. Also adding another heat vent thru the wall into the bathroom. There is an AC vent there (brrrr) but no heat. We've always left the door ajar in cold weather. With the furnace out I can easily add this vent.

[jsmith948]

There have been several posts about Atwood furnaces failing to light.
A new control board fixed ours.
I recommend a board from Dinosaur Electronics.

[kcamp99186]

New Dinosaur board installed, still not working. After more troubleshooting, it seems I have a bad overtemp switch. Replaced the switch and back to normal (hopefully). Still need to run the furnace for an extended time to be sure. How did that switch work part of the time?! RV's can drive me nuts. lol I did check the parasitic load of my battery tender and found it to be less than 10mA. Not sure how accurate my Fluke meter is, so someday I'll check it again with a clamp on unit. If the camper is parked, the tender is powered. Only time it is not is when we're actually camping, so I'm not overly concerned. Thanks to you all. This group is the best!

[atkinsb3]

When this last regulator failed (2-3 months ago) it did affect the furnace. The stove would burn but if I turned on all 3 burners and let them go they were at a reduced flame from normal. As it got worse they would come on and eventually die. I figured the furnace tried to pull more LP than the regulator would allow. New reg and all was good.

My furnace has been doing the same. If I lit a stove burner and then tried the furnace again it would lite. Or if I turned the tanks off and cleared the gas lines the furnace would lite after I turned the tanks back on. I haven't tried lighting all the stove burners to see if they eventually drop or die but plan to do that.

I was thinking regulator but got to reading and was leaning toward the sail switch. Given the option of pulling the furnace out to check the sail switch or trying a new regulator, I think I'll run the burner test and hope it leans toward the regulator.