fan runs all the time... - http://www.hvacmechanic.com/ Forums

Original message

bstm23

72.18.99.229

"fan runs all the time..." , posted Fri 12 Sep 09:38

I've tried turning everything off at the thermostat. I've even removed the thermostat from the wall, but the fan constantly runs. Is this something anyone has heard of? It runs 24/7.

Replies:

klt

198.8.3.42

"Re(1):fan runs all the time..." , posted Fri 12 Sep 11:54

Do you mean the inside blower motor that circulates inside air or the fan outside on the AC unit? I have had a contactor stuck closed outside that kept the compressor and fan running. I have also seen a bad limit switch (detects temperature in heat exchanger) that caused the blower motor to stay on.

bstm23

72.18.99.229

"Re(2):fan runs all the time..." , posted Fri 12 Sep 12:36

I'm talking about the inside blower motor. The compressor outside only kicks on when the A/C comes on.

Is that limit switch a big deal to have replaced or is it a relatively simple task?

klt

198.8.3.41

"Re(3):fan runs all the time..." , posted Fri 12 Sep 12:58

You will want to verify first. On my unit it is easy to access. Turned off power to the unit, checked with volt meter to make sure there was no voltage on the limit switch, disconnected one of the wires on the limit switch and taped the end for safety, turned unit back on to see if fan was off. I then made notes to reconnect exactly, again verified no voltage, removed second wire and taped, my unit had two screws holding the limit switch. Wrote down the manufacturer and model number and found parts store for replacement. Can't remember the circuit off hand but the blower motor relay if stuck closed might also cause this problem. I have not seen one of these stuck before.

bstm23

72.18.99.229

"Re(4):fan runs all the time..." , posted Sat 13 Sep 07:16

I appreciate the info, I'm going to look into this today.