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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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What would cause my heat to come on blowing warm air and

Customer Question

What would cause my heat to come on blowing warm air and then start blowing cold air. It is a Goodman was gas controlling heat.
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: Yes
JA: Do you plan on doing the work yourself?
Customer: Depending on what it might be.
JA: Anything else we should know to help you best?
Customer: It works like it is suppose to and when the heat come on it is warm but after 10 minutes it starts blowing cold air. We changed batteries in thermostat and turn it off for about ten minutes to reset it.
Submitted: 8 months ago.
Category: HVAC
Expert:  gotoman for ac replied 8 months ago.

Russ here, This is usually a bad limit switch which open when the furnace over heats. This caused by low air flow,dirty filters or bad limit switch. When flame goes out does fan keep blowing. On your furnace when this happens if you look thru small hole in blower compartment you will see a flashing LED light. Count the flashes and that will get us in the right area for problem. Fault code chart on door. Russ

Customer: replied 8 months ago.
We got it working by replacing batteries and resetting both thermostat and the unit. Temp back to desired temp now. Thanks anyway.
Expert:  gotoman for ac replied 8 months ago.

Great glad you are back online. Russ