Hi. I have a big problem that is killing me. I have a central Heat and AC unit that works well, but the fan won't seem to turn off. The AC and Heat works well, but the fan just keeps on running. I was gone for 3 months for ARMY business and my wife did not know that this was not working right, so I had to pay a 360 dollar electric bill. I replaced the thermostat and it still seems to keep running. Can someone help me?? I hope it's a cheap fix. Thanks all!

Art

The fan is controlled by a relay and with gas or oil, a limit switch. On newer furnaces the relay is on a control board, difficult to troubleshoot and repair. I would make sure the limit switch is open when the heat is off. If it is, you may be stuck with replacing the board.

Thanks man. It ain't the information that I wanted to hear, but I got to get it fixed regardless. LOL.

Art

I was having the same problem, have an old Ruud furnace in attic, electrician came out, we replaced the thermostat, still problems, then he saw that the housing on the fan exhaust motor housing was cracked. Has to be replaced or carbon monoxide can leak into house he said, 400-700$!! Wonder if Duct tape would do the trick? ;)