Dometic furnace no fire

[Marcela]

Hello all. Have a brand new from the factory slide in truck camper and the furnace is failing me. Service centers look to be nonexistent for the Dometic brand in the midwest.

There is gas to the stove and water heater, they fire instantly.

I have cycled the furnace enough times the propane should be at the burner.

I can hear the spark ignite and the fan starts simultaneously and then the fan stops and nothing. It will do this 4-6 times then quit this process and the red light on the circuit board lights up continuously, which the instruction say is an internal circuit board failure.

So is the circuit board telling the truth and need to be replaced or is there some routine I am missing. I have tried the instructions in the manual and different processes of starting to no avail.

[lmdye]

I am having the same problem on a 2018 Jayco Whitehawk with the Atwood/Dometic Furnance. My repair guy replaced the sail/limiter switch, but says the problem is not fixable. He believes the problem is the new location of the sail/limiter switch over the main burner, with no air flow. And he was right, we worked fine for a week and then failed again. It appears there is a manufacturer problem with these new models. Unfortunately the manufacturer is not acknowledging the problem.....

[dougrainer]

Marcela wrote:
In the end I think it was a bad connection, possibly one of the spade connectors was 50% on and loose. They seemed to be a little loose when connected and I might remember one of them not on 100%.

Tried to replicate the problem and it continues to work fine. I'll keep the suggestions in mind though.

When it fails again, I hope you post a follow up:E As I stated, The sail switch sticks and causes your problem. It is a bad contac IN the sail switch. Doug

[Marcela]

In the end I think it was a bad connection, possibly one of the spade connectors was 50% on and loose. They seemed to be a little loose when connected and I might remember one of them not on 100%.

Tried to replicate the problem and it continues to work fine. I'll keep the suggestions in mind though.

[dougrainer]

Marcela wrote:
Don't think so, but I'll let you know if anything changes.

Chris and I are both RV professional's. If we say to do something, there is a reason:B It will fail again and when it fails, odds are you will be NEEDING the furnace! I have seen this type problem since they went to the new style sail switches and the logic on the newer control boards. It used to make diagnosis difficult, because when you went in to check the various items that cause your type problem, moving things causes the sail switch to start working. Until it decides to stick and fail again. The fact that it did NOT work until you messed with it proves my point. Doug

[Marcela]

Don't think so, but I'll let you know if anything changes.

[dougrainer]

Marcela wrote:
Weirdest thing.

Went out and removed the circuit board to have a look at it, everything looks fine. Pulled the 4 prong plug out of curiosity, nothing looks amiss.

Went back inside and turned it on and the thing fired up as intended. Fan runs prior to ignition and continues to run after flame shutdown as intended.

Only thing I can think of is the removal of the 4 prong plug is a reset or something is intermittent. Maybe it was turned on prior to my possession without the propane being connected. Don't know really.

But for now it works. It's a miracle. Plenty of heat btw.

AS Chris stated, you have a BAD sail switch. When you messed with the connections, you bumped the housing the sail switch is in and it opened. It will fail again, get the sail switch replaced. Doug

[Marcela]

Weirdest thing.

Went out and removed the circuit board to have a look at it, everything looks fine. Pulled the 4 prong plug out of curiosity, nothing looks amiss.

Went back inside and turned it on and the thing fired up as intended. Fan runs prior to ignition and continues to run after flame shutdown as intended.

Only thing I can think of is the removal of the 4 prong plug is a reset or something is intermittent. Maybe it was turned on prior to my possession without the propane being connected. Don't know really.

But for now it works. It's a miracle. Plenty of heat btw.

[Chris_Bryant]

Just to be clear on the sequence, you turn the thermostat on, the blower comes on, does it just run for a few seconds then shut off, or does it run for 30 seconds, then you hear the spark three times, then it shuts off? I get the idea it's the first, and you have a bad sail switch, limit switch or loose wire, and the board isn't seeing power where it should.

[Marcela]

No valve.

No propane smell.

[maillemaker]

just for fun follow the gas line from furnace back, see if theres a shut valve in the line. and google a mobil tech for your area.hope its something easy.

Good idea. There should be a valve near where the gas line hooks up to the furnace. It's possible it is closed.


Steve

[dougrainer]

Go outside where the furnace exhaust vent is located. Have someone start the furnace. See if you smell LP when you hear the furnace do its ignition cycle. That will tell you if the LP valve in the furnace is opening. ANY RV dealer should be a warranty station for Dometic/Atwood. Doug

[midnightsadie]

just for fun follow the gas line from furnace back, see if theres a shut valve in the line. and google a mobil tech for your area.hope its something easy.