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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My furnace will kick on and heat the house but the fan will

Customer Question

My furnace will kick on and heat the house but the fan will continue to blow and cool the house down. Have been having to go down and manually kill the power to get it to stop. When I turn it back on it will not come on until thermostat kicks the heat on but stays running again when heat on turns off. Decided to let it run with thermostat turned off and it did eventually turn off after about 25 minutes.
I did notice the air filter was very dirty. Thought I had replaced it recently but obviously not. Was wondering if you think the limit switch needs replaced.
Submitted: 9 months ago.
Category: HVAC
Expert:  WCohn replied 9 months ago.

Hello, my name is ***** ***** I look forward to helping you!

Expert:  WCohn replied 9 months ago.

This actually sounds like a thermostat issue

Customer: replied 9 months ago.
Have had two new honeywell thermostats that I tried. Same issue happening with each one.
Expert:  WCohn replied 9 months ago.

And was the fan setting set to AUTO?

Customer: replied 9 months ago.
Just a two wire system so has heat and off.
Expert:  WCohn replied 9 months ago.

Well, I'm going to opt out to allow another expert answer.

Expert:  Rick replied 9 months ago.

If the filter was very dirty then you could have had the limit open which would cause the fan to run on and blow cold air. But an open limit will typically shut the burner down before the thermostat is satisfied. Do you still have the same issue with a clean filter?