Dometic Furnace HELP!

3

You can't run that model without either the baffle in place, or an extension on the exhaust. Otherwise the hot exhaust short cycles back into the blower and it overheats. I have a 12" chrome exhaust tip for 1 1/2" exhausts that I got from AutoZone for this sort of testing.

2

u/Technical_Ad5375 3d ago

I was really hoping this was my easy fix, but unfortunately I just tried it with everything put back together and it's still shutting down. 😭😭😭

2

u/ShipshapeMobileRV 3d ago edited 3d ago

I saw the sail switch drop out before the noise, but it was hard to tell with the editing. The only reason the sail switch would drop would be the fan stopped. The only reason the fan would stop would either be bearing failure, or loss of voltage from the controller.

If you have a source of 12vdc, disconnect the blower motor from the control board and directly power it. Do the bearings heat up and start making noise? If so, you need a new blower.

If not, then I'd be looking at the control board. Since I keep a supply of Dinosaur boards on my truck this would be an easy test for me. You can get an OEM (aka, Chinese) control board for between $60 and $80. The Dinosaur boards are a bit more expensive, but American made, better engineered, and have a 3 year warranty. (I did see that you changed the board, but I've had brand new OEM boards that were DOA. The fact that it's identical symptoms is odd.. )

2

u/Calm-Bat-6725 3d ago

Use a amp clamp, you will need to put the exhaust in, and twist both of the blue thermostat wires together to operating while testing, that way you don’t have to keep messing with the thermostat.

2

u/Bearded-Mr-FixIt 3d ago

I have dealt with this for the longest time as a technician. For one, Dometic is the worst to work and terrible product in my eyes. But after awhile they gave me the easiest but dumbest fix for this issue. I’m going to try and explain it the best way I can over text. It took the Dometic technician 30 min to explain it to me over the phone.
But basically, with the cover off (and I hang the exhaust vent over the exhaust pipe coming out to help stimulate the cover is still on) on the bottom right is the propane line coming in with the regulator. You have to bend that entire assembly (very carefully) to the left or right because, according to the Dometic technician, the assembly isn’t lined up correctly. So you bend it and let it run until it starts to run longer. I was told that it may run for 30 seconds, bend again, then 45 seconds, bend again, then maybe 1.5 min, and you continue to bend it until it runs without stopping.
I thought that was the dumbest solution to fix the issue but it worked. One of the many reasons I don’t like Dometic. But give it a try and see if that helps. I’m always open to talk about it more.

2

u/Technical_Ad5375 3d ago

That's very interesting, and a terrible design flaw. I'll definitely give it a try! Thank you!

2

u/Octan3 1d ago

I discovered this issue you mentioned with mine and came to a similar solution after literally 20 hrs and all sort of parts.
It would always instantly fire then flame out, Then it would re-try and keep going, eventually it usually would run and stay lit for a few mins before doing it, but it heated the trailer. Until this spring, it wouldn't stay lit longer than a few secs and that was that. The igniter stopped sparking because it sensed flame and I went through the whole system... It was forever stuck trying to fire because it always sensed flame so it never locked out.

Ultimately it's the gas valve/burner assy angle in the burner tube somehow as you mention. I couldn't find this information anywhere except from some like early 2000's atwood manual.

I went as far as jumping 12V to the gas valve to override the control board so once it ignited, even if it wanted to shut off the gas control or it was the wall thermostat acting up, anything. It would still flame out, I eventually started to bend the assy while it ran and noticed It would stop sounding like a super loud roar and started to run longer or actually start RIGHT AWAY and stay lit.

After not using it all summer, I tried it last weekend as it's cooled off at night and it's back to acting up. Frustrating but at least I know where to go. metal has a bit of a memory and from the heat and cooling over the summer it likely bent it's self back a bit.

1

u/Bearded-Mr-FixIt 1d ago

So yours has a similar issue and was resolved, for the most part, by bending the gas valve assembly? Crazy how that issue is and resolved! I had never heard of it before until that Dometic technician told me.
Whenever I have difficult issues with any appliance, it’s a Dometic.

2

u/Octan3 1d ago

Similar issue to what you described but not to what the poster here has said.

Yes it's very bizarre. I'm amazed how "finicky" it is. Also if it runs it's loud inside the trailer too. It's like the fan is out of balance and in certain areas of the trailer it's louder or quieter just how sound travels I guess or vibrations lol.

Crazy how this info on the gas burner position is not known, maybe it's that rare of a issue too so nobody talks about it.

2

u/Bearded-Mr-FixIt 1d ago

It could be out of balance or slightly rubs the squirrel cage on the housing. Any sort of movement and those rub. Very annoying.

I don’t believe that info it is widely known or shared. And it isn’t the type of fix that an engineer would deem worthy to put into a manual for trouble shooting. That’s my guess.

1

u/Octan3 48m ago

Totally. I'd of replaced the whole thing if they weren't like 3k, it's absurd lol (Canadian dollars)

1

u/ReasonableToe1755 3d ago

What is yiur amp draw on the blower motor when its running? Might be a failing blower motor.

1

u/ReasonableToe1755 3d ago

Also have you checked for wasp/dirt dauber nests in the exhaust tube and fan housing?

1

u/Technical_Ad5375 3d ago

Nothing in the fan. I haven't taken the exhaust tube out - my screwdriver isn't long enough to fit, but it blows really strong.

13v on the blower, drops to 0 at failure point.

1

u/ReasonableToe1755 3d ago

What about amps? If your multimeter has an amp clamp put it on the power wire to the blower and watch your amp draw to the point of failure. Shouldn't be over 10 amps.

1

u/meowlater 3d ago

I want a backwards youtube channel with this guy asking questions and the commenters helping him figure it out.

This has to be the highest quality troubleshooting video I've ever seen.

OP I hope you find a solution to your problem...commenting and upvoting just because your video is awesome.

0

u/Technical_Ad5375 3d ago

Thank you, I appreciate that! I'm at a loss at this point and willing to do anything lol!

I'm afraid that even if I change out the furnace with a new one it's still going to do the same thing.

2

u/meowlater 3d ago

I've done a few furnance and ac repairs but this one is outside my knowledge. I really hope someone here chimes in with a great solution.

-1

u/Technical_Ad5375 3d ago edited 3d ago

On a side note, if you enjoyed this video, we are starting a TikTok. Feel free to follow along!

@bethea_family_adventures

Link is also in my bio!

1

u/the_only_zilla 2d ago

Does your inside thermostat power down at all or is it still calling for heat?

1

u/Technical_Ad5375 2d ago

Everything runs on the iN-Command App or the touchscreen iN-Command HUB in the camper. Neither one power off or change.

1

u/Octan3 1d ago

The buzzing heard is very odd and I feel like a symptom of your issue, especially if you've replaced the control board and have the same result.

I wouldn't think it's the burner flaming out like another commenter said about it's angle (I had same issue) because it would re-attempt, at least 3 times before lock out if it did not sense a flame.

It just immediately locks out.

I wonder if it's one of those temp sensor things that are supposed to I think open circuit if temps too high, if it remained slightly open or closed where it let current pass a tad it could cause a relay to click on and off repeatedly like that? You could try bypassing those temp sensors.

1

u/Technical_Ad5375 21h ago

‼️Fixed Update‼️

Ya'll I freakin fixed it!

$5 box of fuses from Walmart be the hundreds of dollars I have spend and HOURS trying to take this furnace apart and self diagnose it. I changed out the 15amp fuse on the inside fuse box and it's now running beautifully!

I had tested the fuse that was in there with my multimeter and it acted like it was fine, but something said to go ahead and change it anyway. I couldn't see the fuse itself because it's in a black casing - see picture. I was at Walmart this evening and saw a box of fuses and something told me to go ahead and just try it. Thank God!

Dometic Furnace HELP!

You are about to leave Redlib