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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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This problem has been looked at twice by technician but

Customer Question

This problem has been looked at twice by technician but still not corrected. When switching from heat to cool or cool to heat the unit will not work correctly unless a complete reset is done (shutting down power, wait 10 minutes, restart power.) Now during heat season when the unit is restarted it will produce warm air until the thermostat is satisfied, the warm air stops being produced, but the fan continues to run even when the thermostat is on auto setting and blows cool air. It will run until I physically turn down the thermostat setting then the fan stops. When the thermostat calls for warm air again the fan starts but blows cool air. Fan will run and blow cool air until I turn it off. If I reset the power at this point it will repeat the same pattern.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, so far it sounds like a printed circuit card going bad.

Has it been this way from the very beginning or did this situation develop later.

Use a hair drier to slowly warm the printed circuit card up to120For a bit warmer, but not over 140F... if there is any change in the error codes or other furnace behavior... the card has a cracked micro circuit that opens and closes as the card expands and contracts... that proves a bad printed circuit card.

No change however does not prove the card is good however... but any change proves the card is definitely bad.