dometic furnace short-cycles

[plgamble]

I have an outback 210 URS, 2018 model. In the spring I put in a new board from Dinosaur, and a sail switch, to resolve a prior problem. I driveway-tested every morning for a week, to confirm. Now, I was checking the trailer out for a trip, and noticed the problem: Thermostat calls for heat, blower comes on. Then, shortly, furnace fires up as usual, and stays firing for 10 or 15 seconds, then firing stops, but blower stays on. Then, 10 or 15 seconds later, it fires up, then stops, and the cycle repeats, and so on. It does make heat.

The result is the same with any combination of old/new board/sail switch. I by- passed the thermostat with same result. I don't have an access door, so I cant see the error code on the board with the gas connected. But, I did add a service loop to the power, and without gas connected, the factory board led was solid green while firing, solid red while not firing.

I believe the dometic warranty is 2 years, but I prefer to not go to the dealer. Any advice will be appreciated!

Phil

[ChuckS]

I winder if thermocouple is sensing the flame... since you’ve got ignition and it’s firing the HI Limit circuit is good unless it’s opening up after it lights off

[plgamble]

thanks, chuck. Im going up to lowes to see if I can rig up a safe, and possibly flexible gas extension, so I can read the codes live. Yes, the gas valve, maybe debris, and the Hi-temp sensor if its auto reset. I would rather replace parts, and even just buy a new furnace, before I go to a dealer...….. FYI, for a bench test, a 12 volt dewalt battery will run it at full speed.