Furnace comes on by itself???

[KOZKO]

I went out to the trailer today and the furnace was ON!?!?! It's the standard analog Coleman-Mach (black). It was in the off position. I pulled the fuse and it went off - duh. After reinstalling the fuse the furnace stayed off. I put temperature all the way down to 55, verified in off position and went in the house. I came back out to check about 15 minutes later and the furnace is ON again???? Anyone ever see this or know what to do?

[Eastham]

Maybe the thermostat is bad .Does it go off if you put it in the on position?

[ctbruce]

Was the furnace blowing hot air or was just the fan running? If just room temp air, try setting your thermostat to auto instead of fan. May work. I hope it does.

[KOZKO]

Now, when you put the fuse back in the furnace runs heat and fan constantly! Even with the wall thermostat completely unwired. I follow this guys advice cut the blue wire and now at least the air-conditioner works. I found this on Forest River site with a Google search this guy says “There are two wires that connect for a heat call in the thermostat. One is 12v and the other is the heater circuit.

Somewhere in your system these wires my be shorted together, or intermittently shorting together.

Where the wires go into the heater find the non-12v thermostat wire and disconnect it. If the problem goes away, you'll have to chase out the wires for contact. Screws run through them, stripped insulation etc. If that does not solve the problem, its probably in the furnace.”

[chuckster57]

If the furnace was working before, I suspect the control board.

[JRTJH]

If the furnace was working before, I suspect the control board.

That was my thoughts also. Wires don't just move from one contact to another. Granted, there may be some remote chance that a screw through a wire "finally" shorted it out. But I'd guess if that happened, it was from a unicorn rubbing against the harness..... IOW, chances are it ain't a wiring problem.... Control board corrosion, twisted and broken printed circuit, overheated and intermittent diode/transistor ???? I'd have to agree with chuckster, it's very likely the control board.

[KOZKO]

Well I have the extended warranty (hopefully that works out). It worked fine all last weekend and then apparently sometime since we got home it went nuts because I had 1-1/2 tanks of propane and now I only have 1/3:banghead:

[KOZKO]

SOLVED!!
Found the 12VDC + was shorted (staple somewhere I guess) to the furnace on wire!