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spyder9669 · May 23, 2006, 10:23 AM

Well, we moved into this mobile home about 3 weeks ago. We have our a/c and oil heat connected to one thermostat. It was all working fine up until a few days ago. All of a sudden, the heat would not shut off at all. Eventually it got up to 90 degrees in here and I just opened the door to the furnace or whatever and just unplugged the motor. After a few minutes it went off. But when I plug it back in, it starts right back up, even though it is turned off on the thermostat. The only time it will stop running is when its unplugged. The a/c works fine I can turn that on and off with the thermostat... but the heat is all messed up. I can actually have both the heat and a/c running at the same time now as long as the heater motor is plugged in and the a/c is turned on with the thermostat. Obviously, there is a huge problem here... someone please help me because we can't really pay someone to come deal with it right now

tkrussell · May 23, 2006, 04:59 PM

Either the red and white wires from the stat to the furnace are pinched someplace, causing a short , or the stat is defective. Take these two wires off the stat, if the heat continues, the wires are shorted, if not, replace the stat.

spyder9669 · May 23, 2006, 08:48 PM

Originally Posted by tkrussell

Either the red and white wires from the stat to the furnace are pinched someplace, causing a short , or the stat is defective. Take these two wires off the stat, if the heat continues, the wires are shorted, if not, replace the stat.

There is 2 sets of red and white wires...

tkrussell · May 24, 2006, 02:54 AM

Then work with the pair that should take care of the heat, usually R and W terminals on the stat

spyder9669 · May 24, 2006, 07:41 AM

OK I disconnected them, and the heat still runs. I think I would have rather just replaced the thermostat. Considering the wires are running either above the ceiling, or in the walls somewhere, how am I supposed to check for a short?

tkrussell · May 24, 2006, 09:23 AM

Since you have disconnected the stat, and the heat is still running, you probably have a short in the wiring, anywhere fromn the stat to the furnace.

Or a relay is stuck in the furnace.

To check for a short, you need to trace the entire length of the cable looking for a something pinching the cable, or a nail or screw driven through the cable.

May be easier to just run new cable.