I have my thermostat set on HEAT.... and my FAN set on AUTOWhen thermostat reaches set temperture of 70degrees.....The furnance itself,SHUTS OFF.... but the Fan keeps blowing.I replaced the thermostat.. and the FAN,still wont turn turn OFFAny ideas what is wrong ??? Thanks !!!
either the fan relay in the furnace is bad or the fan switch is bad....the relay is what changes the speeds between heat and ac if this goes bad fan would run all the time on high speed normally......the fan switch is activated by heat or is electronically controlled...if it is electronically controlled the board determines what speed the motor comes on by the way you have the thermostat set...if it is activated by heat it could be one of two types..1 fan/limit this is a square box that controls both the fan and limit it is usually mounted on the firebox. 2 fan sensor, small oval shaped device with two wires on it and will have the letters and numbers on like f-120 or f110, this will also be mounted on the firebox...
nothing. the stat shuts off the burner, and the heat exchanger is still hot, so the fan stays on until the heat exchanger cools. maybe if the fans stays on too long, you need to adjust the anticipator on the stat.
The fan on a warm-air furnace will continue to run for a minute or so after the demand for heat is satisfied. This is to purge the air ducts of the warm air that remains in them once the heat shuts down. However if the fan runs continually, you have another problem. A licensed heating technician will have all the equipment to test for the possible reasons your fan won't turn off. I would take care of it sooner rather than later. You don't need the fan motor overheating.
It sounds like the fan/limit switch is bad. For more info including a troubleshooting guide, check out the furnace page at my source.
Snake-take the furnace front cover off , there should be a fan control/ limit switch - to recog. it -it should have a little wheel on it with a couple of adjustable pins on it -when the room temp. shuts the furnace off see if that control has turned counterclockwise, back across the pin on the left end if not you might be able to clean it and help..... If I was there I would help you BUT I AIN'T SO I WON'T.. (Good luck) when you take the cover off there night be a contact switch on the furnace -so It won't come on w/o the cover--just push the switch in to make contact. One more thing Snake -I hate to get on your bad side-after all you are a snake- but you are sure the stat is hooked up right. they have an auto on off fan on fan off on most stats
