Intermittent Furnace Shutdown

[tlhagood]

My Dometic furnace is working the majority of the time. About once or twice a night it will turn blower on but will not fire. If it does it when I am awake I can turn off furnace with the Jaycommand app and turn it back on and it will usually start and fire. If I am asleep, it will stay off sometimes for about an hour and then will refire on its own. I have a separate wifi temperature system that I can monitor temperature and see it on a graph. I can tell by the graph when it shuts off and when it refires. I have checked the sail switch for debris and dirt. It was really clean. Unit is only about a year old.

[RogerR]

Try Googling "dometic rv furnace diagnostic" this brought up several ideas on why it is not firing.

Add the exact model furnace which is hopefully somewhere you can find it and not buried in the back.
Common causes to my knowledge are, bad board, bad flame sensor, LP pressure problems, loose wires, poor voltage to the furnace, loose wire at thermostat and bad thermostat. Odds are it is the flame sensor, sail switch going out or board.

Based on past posts I would get a sail switch, about $25, and swap it out. If it still is not working you have a spare. Pull board and check voltage, connections, look at flame sensor, etc. while you are in there.


Many posts about this problem and you can also search in the search bar above for how others have solved the problem.

[tlhagood]

Originally Posted by RogerR

Try Googling "dometic rv furnace diagnostic" this brought up several ideas on why it is not firing.

Add the exact model furnace which is hopefully somewhere you can find it and not buried in the back.
Common causes to my knowledge are, bad board, bad flame sensor, LP pressure problems, loose wires, poor voltage to the furnace, loose wire at thermostat and bad thermostat. Odds are it is the flame sensor, sail switch going out or board.

Based on past posts I would get a sail switch, about $25, and swap it out. If it still is not working you have a spare. Pull board and check voltage, connections, look at flame sensor, etc. while you are in there.


Many posts about this problem and you can also search in the search bar above for how others have solved the problem.

Thanks for the info. I was thinking sail switch would be dirty or obstructed but it wasn't. Based on posts looks like they are subject to issues even if clean. Puzzling part is that it works the majority of the time.

[tlhagood]

RV dealer tech finally came out and solved issue. It was a cracked insulator on the ignitor. The crack wasn't bad enough for it to not work at all. Apparently if ignitor was cold it would ignite. If it was really cold out and it needed to cycle more often, the built up heat would let it spark at the base of the ignitor and not the tip. This intermittent issues will drive you crazy. Hopefully this will help someone else with similar s symptoms.

[Jagiven]

First read, I was thinking sail switch. That issue would take a bit longer to diagnose.

Glad you got is solved

[Radar57]

Anyone that has a furnace I would recommend searching YouTube for My RV Works for a 2 part video he did titled "Follow the Furnace Fault Road". It is the very issue the OP posted.

He goes into great detail on how the furnace works. The interesting part is where he talks about after the furnace is operating that the control board send a milliamp signal through the igniter. The carbon in the fire creates the the electrical path, jumping the gap of the electrode, back to the board and that's how it knows to keep operating. If the gap is to big or the igniter is damaged, as is the case in thus situation, the furnace shuts down. Same principle applies with the water heater. I believe he was discussing the Dometic units but I could be wrong on that. Anyway it is some good info.