Furnace problem

[Bnrc73]

2010 Montana 3400RL. Furnace worked fine for 4 months in Texas. We’re out again a month later and my furnace is acting up. You start it up and it runs for about a minute blowing cold air then shuts off. Turn it off and back on with same result. Doing that several times it will finally starts throwing heat and works fine. I replaced the mother board a couple years ago with a dinosaur board, so I don’t think that’s the problem. Anybody else have this happen? Thanks in advance.

[jsb5717]

It's possible that you have a dirty or faulty sail switch. If you have easy access to it I would pull it out and clean it. That will often solve a pre-ignition problem. It might be just dirty enough to prevent ignition but still occasionally make good enough contact to work. If that's what it is then it's usually just a little piece of lint that needs to be cleared.

It's also possible that it's going bad and needs to be replaced. That's more rare but possible.

[ChuckS]

Agree with most likely cause in your case is intermittent sail switch.. Your furnace is most likely Dometic Atwood AFM series.. If you have outside access to furnace the task is a piece of cake.. Newer Montanas do have outside access panel to furnace..

You CANNOT CLEAN a sail switch... Yes . you can remove any crap that might be around the outside area of the paddle arm but you aren't getting to the root of the issue without taking the sail switch apart.. The case is riveted together.

Spraying contact cleaner, canned air, etc is a feel good repair and the issue will come back quickly again and you wont have heat..

Video i put together showing why its a joke if someone cleans a sail switch.

https://youtu.be/Neg5E0WemgY