So we have been staying in our camper and we replaced the propane regulator about 2 months ago and the heat was working perfect now all a sudden the heat doesn't kick on when its set to a certain temperature and just randomly kicks on an blows cold air sometimes hot. We replaced the thermostat but that didn't fix it. We have propane to our stove and the exhaust from propane outside is hot so it is igniting, a furnace guy said it could be the furnace circut board but where do I find that also could it be anything else??


Well-known member
The random nature suggests several possibilities. If the cold air scenario lasts for about 25 seconds and then the blower shuts down, it could be the sail switch. If you have the air return or any of the ducts blocked, that could be causing a sail switch random failure.

If the cold air, when you get it, blows continuously, it could be the high limit switch intermittently failing.

You might have a loose wire. There are typically 4 wires from the trailer wiring connected to the furnace wiring. A bad connection on one of those could give you intermittent results.

It also could be the control board. If your furnace is mounted horizontally, it's on the left side. The 4 screws holding the exterior cover have to be removed to get a look. There are probably 2 long screws that mount the furnace assembly to the frame that's alongside the furnace.

To get at the wiring or control board, you probably will have to disconnect the propane supply and then gently pull the unit out a few inches. Handle everything gently.

I'd inspect the wire nut connections first before going to the control board.

The sail switch can be accessed by removing the large half round cover over the blower assembly.

The high limit switch is on the other end and I think you might need to completely remove the furnace to get to it.


Well-known member
Here is a link to the Suburban Service Guide from our forum library. I am assuming that it is a Suburban furnace (most common).

Besides OEM Suburban, there is a long established and well regarded company making its own versions of RV refrigerator and furnace circuit boards - Dinosaur Electronics.

Do a Google search on "Suburban RV furnace circuit board" . You need to know your furnace model number, and check the details in any web listings, as everything is not completely compatible.


Prolifically Gabby Member
When ours did that a couple of years ago, it was the circuit board. Since it was at the end of our summer season (northern Michigan can be chilly in late September) I took it to the dealer to diagnose and fix it.

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