I have a carrier furnace. The blower is not shutting off, even when the thermostat is set to off. Could it be the thermostat unit? The relay? The circuit board on the carrier? A fan switch somewhere? Where is the best place to start diagnosing this problem? And in what order should it be done? Thank you for any guidance you can offer.

Defective fan switch or relay

Fan switch at t-stat in on position?


Fault codes present? Need more info please

Well, it turns out there is a reset switch on the triangular flue. A circuit seemed to have tripped this reset switch for unknown reasons. I was reading the schematics of a carrier furnace similar to mine and they showed two reset switches in the lower blower unit. After taking out the blower unit and NOT finding any reset switches, I called a serviceman. Watching him check the circuit board, wires, etc. and seeing him find this reset switch was almost unbelievable. He hit the reset and the furnace blower stopped and the flames went into where they belong and then the blower went on and worked fine ever since. Good thing, too, because everything on the circuit board is soddered and would have to be replaced. Parts roughly 200 plus labor. Luckily my serviceman is an honest hard working soul and only charged me half of the call fee because of it being such a silly fix. Thanks to all who tried to help. It's cold in Chicago and I couldn't wait any longer to get the fix on my own.