When I put my electronic thermostat to the FAN position, the AC runs continuously (even if I have the HEAT/COOL switch OFF!).

I have checked the wiring on the thermostat and on the furnace control connections -- it all seems to be correct. Could it be a faulty thermostat?

It could be that the control wire for the fan "G" is shorted or touching the cooling wire "Y" either in the back of the thermostat or at the furnace or in attic.

It could be that the control wire for the fan "G" is shorted or touching the cooling wire "Y" either in the back of the thermostat or at the furnace or in attic.


OK -- thanks. I will check that more closely.

My guess is that it is probably not your thermostat.

When I put my electronic thermostat to the FAN position, the AC runs continuously (even if I have the HEAT/COOL switch OFF!).

I have checked the wiring on the thermostat and on the furnace control connections -- it all seems to be correct. Could it be a faulty thermostat?
If you have your fan in the in the on position and not auto your a/c will run all the time.

My guess is that it is probably not your thermostat.
I checked and you are correct -- it is not the themostat (I had an old one I hooked up). Also, no wires shorted together. Any other suggestions?

If you have your fan in the in the on position and not auto your a/c will run all the time.
Unless I am mistaken, when the switch is in the FAN position, the FAN should run all of the time and the AC compressor should still only run when cooling is called for.

Cdehrlich, you are correct the a/c will cycle and the fan will run continuously, if the a/c runs continuously then try disconnecting the two thermostat wires going to the outdoor unit , if it still runs then the contacts in the outdoor unit might be stuck together (this happens) Turn off power when trying to fix contactor.