Hello. I have a Carrier Weathermaker 8000 TS (gas) that is about 7 years old.

I was running the furnace fan (not the AC or heat) one day last week (to circulate the cool air in our basement) and it wouldn't shut off until I killed power to the unit. I have tested the furnace fan a few times since then and I have had the same problem. I have also tested both the AC and heat and both seem to be working but, again, the fan will not shut off at the end of the heating or cooling cycle.

The thermostat seems to be working OK so I am thinking that it is a problem with the fan control or the fan itself. Does that sound about right? Is there any easy fix (like cleaning a sensor? Or an easily replaceable part), or should I be calling in the pros?

Cheers
Garth

Yes you are right odds are it is the fan control board. The relay in it is sticking.

Thanks, that's good to know... shouldn't be too pricey then. Anything that can be done other than replacing the board?

Cheers
Garth

Try disconnecting the "G" wire from the circuit board. If the fan continues to run, the board is the most likely culprit. If not, check your thermostat and control wiring.