hello to every one, maybe someone can help with my problem. my furnace blower motor will not stop running. when the t-stat calls for heat it blows warm air after the heat cycle the blower blows cool air,so it's kind of working against its self. the only way the blower will shut off is if you turn the power disconnect switch off.this is also the same issue in the warmer months when using the a/c

labman

Sounds like a stuck relay. Unfortunately on all but the oldest furnaces, it is on a big bucks control board and difficult to do much except replace it.

letmetellu

This may sound silly but I see it all the time. Make sure that the fan switch on your thermostat is on "AUTO"

letmetellu

Oh I should have added this. Take the cover off of the circuit board and you will see two relays, tap each one lightly with a screwdriver handle. Like Labman said sometimes relays stick, and also sometimes tapping them will unstick them......tap lightly.

labman

Tapping the relay is a good diagnostic. If it unsticks the relay, you know it was the problem. Usually they stick again soon.

mizlady1255

I have the same problem except my heat will shut off if I manually drop the desired temp below the room temp.The heat will come on if room temp drops below desired temp automatic .If desired temp is 68, room tempt will go to 67 and keep running . I'm trying a new thermostat. Hope it helps-Power bill high this month.