Furnace trouble

[92xj]

Well, It's me again, starting another thread about an issue and looking for suggestions. Whenever I learn it all, I promise to post helpful threads instead of looking for help threads.

Went out for the first trip of the year, the week before prepped everything and made sure everything was working. Furnace worked and fired up and heat was blowing. The day before leaving, I filled all the propane tanks and remembered we have the option to bluetooth into the TT and control it on the phone, so I downloaded that app and ran through the controls in the drive way. All worked and seemed well.

We get down to the area on the NF I want to camp and get set up. In the evening, I turn on the furnace and warm it up for the kids to get into bed. The blower turns on for 10-20 seconds and then turns off. Normally during that 10-20 seconds of the blower running, the furnace kicks on and you get hear the roar of the flame. This time, the roar didn't happen and no flame/heat. Figured it can't be electrical as the fan kicked on and ran, but I checked all fuses, and good to go. The next thing has to be propane. Check all my other appliances and the worked fine. Fired the outside grill up out side to make sure propane was making it there, and it was. Turned everything off, unplug the propane bottles, sat and drank a glass of wine, then went back, hooked up the tanks, turned on the power, checked the stove, fridge, water heater and grill, all fired up and ran just fine on propane. Turned them all off and tried the furnace again. Fan came up and no furnace/heat. Got out the manual and their trouble shooting says if the fan works, there has to be air in the lines and to purge them by running all other appliances. I did that and still nothing. I have no idea what to try next.

The last thing I did before having issues was install that stupid app to control the TT via bluetooth. I would assume it is just coincidence but it boggles me that this starting happening after that. I just can't see how it would happen though.

Hit HVAC button. TT was at 55 degrees, Hit Heat, Gas source and Auto Fan. Hit the up arrow to 63 to have the furnace kick on and heat. Fan only, not heat. There is no schedule set on the display or app. I don't have the option to change the source from gas to electric.

2019 Cougar 25BHSWE, Dometic DF Series furnace. Not sure of the model but the instruction booklet has 13 models DFSAD12 - DFLA40.

[jsb5717]

There’s more than one potential reason for that issue. However, the first and simplest thing I would check is the sail switch. They rarely go bad (although they can) but they can get some lint caught in them preventing the furnace from igniting. Hopefully your furnace is easily accessible from the exterior so you can quickly get to that switch.

Give that a look. Pull it out, clean it, and put it back. If that doesn’t solve it please let us know.

Edit: as an FYI, propane isn’t the issue with those symptoms. The furnace isn’t even attempting to ignite so you currently have a pre-ignition issue.

[JRTJH]

A couple of questions:

When you were at home checking things out, I'd guess you were on shore power?

You said "got down to NF (national forest ???) which would indicate probably battery power ????


If so, I'd suspect that over the winter, you "lost a battery" and are feeling the effects of shore power works well, battery power can't turn the fan fast enough to close the sail switch.....

So, think back to the two occasions, were they both on shore power or one on battery power ???

[92xj]

You are correct that NF is national forest and was on battery power, but also ran the generator and tried and still nothing. I run two Trojan 6 volts with a 200w solar panel. I would doubt that I didn’t have enough power in the woods, BUT I will test that theory. Got the Tt parked and will hook up to shore power tomorrow evening after work and see if it fires up. Thanks for the thought and idea.

[92xj]

Originally Posted by jsb5717

There’s more than one potential reason for that issue. However, the first and simplest thing I would check is the sail switch. They rarely go bad (although they can) but they can get some lint caught in them preventing the furnace from igniting. Hopefully your furnace is easily accessible from the exterior so you can quickly get to that switch.

Give that a look. Pull it out, clean it, and put it back. If that doesn’t solve it please let us know.

Edit: as an FYI, propane isn’t the issue with those symptoms. The furnace isn’t even attempting to ignite so you currently have a pre-ignition issue.

Roger that. Your edit section makes sense. I have no idea what or where a sail switch is, but I will google tomorrow and then tomorrow evening dig around in the tt. My furnace is located under the fridge, at least I think that is what I was looking at. I pulled the “wood” panel off and found the box with the 4 ducts coming out of it. It’s also the location inside the tt that lines up with the exhaust port on the outside. The box is completely closed up with nothing seen on the outside of it besides the ductwork.

Thanks for the input and suggestions gentlemen. I will do my research on location of the sail switch and take some pictures and post up what tomorrow brings.

[Bustinbeards]

Sounds exactly like a sail switch symptom/issue. I had the same issue in our 2019 bullet. Seems like they had quite a few bad sail switches around that time. 50$ Part, I ordered from dometic, very easy to replace. I have a thread where I documented the replacement and took pics.

https://www.keystoneforums.com/forum...ad.php?t=49740

[ChuckS]

Images and Info for your Dometic/Atwood Furnace... Location of sail switch and what it looks like, fault error codes that will be displayed on the furnace control board for the Atwood series furnace and location of the control board.

[92xj]

Thanks!!!!

From my looking over the weekend, it looks like I’m going to have to remove the duct work and unhook the furnace to pull it out of its cubbyhole under the fridge to even see the side that has the control board and sail switch, which’s means I will have it unhooked and the led lights won’t show me anything, unless I’m missing something.

Also, Does the furnace attach to the metal plate on the outside? Will I need to unscrew it or does the inside pipe press into the outside cover deal?

When I get home from work, I plan to head out and start taking things apart, will grab some pictures to post when/if I get stuck. These comments above are based off my memory from 24 hours ago, lots of things run through my head making that memory foggy at times.

[flybouy]

I'd buy a new sail switch and have it on hand. It's a known issue with sail switch failures around that time your trailer was made. I've read several accounts of folks pulling out the furnace, cleaning the sail, putting it all back together and it working for a short time then failing again. The switch doesn't cost that much and IIRC they changed the switch slightly.

[92xj]

Roger that.

My plan is to get it pulled to read/confirm the part number, I’m the current sail switch. Then order two new ones and not even worry about cleaning the current one. Just tossing it, installing the new one when it arrives and throwing a backup in the trailer tool box.

[flybouy]

Having a spare will pretty much guarantee you'll never need it. I think part of the issue was debris getting into the micro switch itself. They are riveted together and just not worth attempting to get them clean on the inside.

[92xj]

Originally Posted by Bustinbeards

Sounds exactly like a sail switch symptom/issue. I had the same issue in our 2019 bullet. Seems like they had quite a few bad sail switches around that time. 50$ Part, I ordered from dometic, very easy to replace. I have a thread where I documented the replacement and took pics.

https://www.keystoneforums.com/forum...ad.php?t=49740

Just had a chance to read your linked thread. That is great info and helps get my mind in the right headspace to tackle this.

A few questions...
Did you just unscrew the hose clamps on the duct work and leave them in place just disconnected from the unit, or did you pull the duct work out of where the go down into the floor? I hopefully know the answer to this, but just confirming.

After turning off propane bottles, bleeding the system dry, disconnecting the battery, and then unscrewing the propane line, did the unit just pick up and pull out? Was it connected to the floor at all? When I looked in there this weekend, I do not remember seeing the exposed wires , the vent or the reset switch like I can see on yours. Maybe there is a thin metal cover plate that I will take off first that will expose those things?

[Bustinbeards]

Yes I just loosened the clamps and tucked the ductwork down out of the way.

The wiring is zip tied up with enough slack to pull unit once you cut zip tie, without having to unwire/rewire.

Yep. After the ducts and gas line were disconnected just pull the unit away from the outside wall and lift.

The outside vent just slides onto the exhaust pipe on the back (wall side) of the furnace. Might have to lift furnace slightly when reinstalling to get it lined up properly.

[jsb5717]

FWIW, when I pulled the furnace on a friend's RV I unscrewed and pulled the vent off the exterior first to avoid the realignment issue. It was very easy, then, to put the furnace back in place and realign the vent from the exterior before screwing everything back down. YMMV

To the OP...it sounds like you don't have exterior access to the furnace so if you do have to pull the entire furnace out then YES, for sure, just replace the sail switch with a new one to avoid having to do it all again right away. The good news is that pulling the furnace really isn't that bad and once you've done it it will be much easier if you have to do it again down the road. Let us know how it goes.

Also, keep in mind that you might not be able to undo the gas line until you pull the furnace out. That will require that you will have to flex the copper gas line as you pull the furnace out. If that's the case then there will be (or should be) plenty of length to allow for that. Be careful to NOT over flex the copper pipe. Anyway, that was my experience. Hopefully your access to the gas connection will be better.

[92xj]

Originally Posted by jsb5717

FWIW, when I pulled the furnace on a friend's RV I unscrewed and pulled the vent off the exterior first to avoid the realignment issue. It was very easy, then, to put the furnace back in place and realign the vent from the exterior before screwing everything back down. YMMV

To the OP...it sounds like you don't have exterior access to the furnace so if you do have to pull the entire furnace out then YES, for sure, just replace the sail switch with a new one to avoid having to do it all again right away. The good news is that pulling the furnace really isn't that bad and once you've done it it will be much easier if you have to do it again down the road. Let us know how it goes.

Also, keep in mind that you might not be able to undo the gas line until you pull the furnace out. That will require that you will have to flex the copper gas line as you pull the furnace out. If that's the case then there will be (or should be) plenty of length to allow for that. Be careful to NOT over flex the copper pipe. Anyway, that was my experience. Hopefully your access to the gas connection will be better.

Thanks. And yep, you are correct that I have no access panel on the outside to open. The only thing I have out there is the exhaust port. My plan was to not mess with that so I don’t need to reseal it but if it makes removal and installation easier, then I will and reseal when done.

I am hoping I’ll be able to get a wrench on the gas line and remove it in place to avoid bending the line, we shall see what happens this evening.

Thanks again for the thoughts and opinions. They are all a huge help.

[ChuckS]

Watch this video I made a while back.. about half way thru I take apart a sail switch and show you why you cannot possibly clean a sail switch with a can of contact cleaner, air, etc...

get the new sail switch in hand before you yank the furnace out and use a multimeter in the Ohms position and check for switch continuity across the two wire connections on the new switch BEFORE you install it.. Gently move the paddle arm and you should have continuity when the contacts inside the switch mate..

If so the the switch " should be good to install "

https://youtu.be/_Pf_KC_xwpM

[92xj]

I would order a new one before removal, but I am not exactly sure what the part number is for my sail switch. My two Dometic furnace manuals only say "For replacement part information, see the DF Series Furnace Parts List." Yet, both don't contain a Parts List. I also don't exactly know what DF series furnace I have. So, I will just pull the currently installed sail switch and find the part number on the switch to order.

Will watch your video shortly.

[Bustinbeards]

Originally Posted by 92xj

I would order a new one before removal, but I am not exactly sure what the part number is for my sail switch. My two Dometic furnace manuals only say "For replacement part information, see the DF Series Furnace Parts List." Yet, both don't contain a Parts List. I also don't exactly know what DF series furnace I have. So, I will just pull the currently installed sail switch and find the part number on the switch to order.

Will watch your video shortly.

What is the model of your furnace? Should be a sticker like this

If this is the same as your model the sail switch part number I ordered is 33082. 29.17$ + shipping=46.81$ you may come out cheaper if you can find one local and not have to pay the $$$ for shipping from dometic

[jsb5717]

Or on Amazon

https://www.amazon.com/Dometic-33082...s%2C153&sr=8-2

[Chrispl36]

Originally Posted by 92xj

Well, It's me again, starting another thread about an issue and looking for suggestions. Whenever I learn it all, I promise to post helpful threads instead of looking for help threads.

Went out for the first trip of the year, the week before prepped everything and made sure everything was working. Furnace worked and fired up and heat was blowing. The day before leaving, I filled all the propane tanks and remembered we have the option to bluetooth into the TT and control it on the phone, so I downloaded that app and ran through the controls in the drive way. All worked and seemed well.

We get down to the area on the NF I want to camp and get set up. In the evening, I turn on the furnace and warm it up for the kids to get into bed. The blower turns on for 10-20 seconds and then turns off. Normally during that 10-20 seconds of the blower running, the furnace kicks on and you get hear the roar of the flame. This time, the roar didn't happen and no flame/heat. Figured it can't be electrical as the fan kicked on and ran, but I checked all fuses, and good to go. The next thing has to be propane. Check all my other appliances and the worked fine. Fired the outside grill up out side to make sure propane was making it there, and it was. Turned everything off, unplug the propane bottles, sat and drank a glass of wine, then went back, hooked up the tanks, turned on the power, checked the stove, fridge, water heater and grill, all fired up and ran just fine on propane. Turned them all off and tried the furnace again. Fan came up and no furnace/heat. Got out the manual and their trouble shooting says if the fan works, there has to be air in the lines and to purge them by running all other appliances. I did that and still nothing. I have no idea what to try next.

The last thing I did before having issues was install that stupid app to control the TT via bluetooth. I would assume it is just coincidence but it boggles me that this starting happening after that. I just can't see how it would happen though.

Hit HVAC button. TT was at 55 degrees, Hit Heat, Gas source and Auto Fan. Hit the up arrow to 63 to have the furnace kick on and heat. Fan only, not heat. There is no schedule set on the display or app. I don't have the option to change the source from gas to electric.

2019 Cougar 25BHSWE, Dometic DF Series furnace. Not sure of the model but the instruction booklet has 13 models DFSAD12 - DFLA40.

Check the resettable fuse. I had a bad one. You can check by installing a 25 amp auto fuse.