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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have an Amana Air command 80. When you turn on the heat it

Customer Question

Hi. I have an Amana Air command 80. When you turn on the heat it comes on and does everything correctly except when it get to set temp on thermostat it won't stop. Fan continues blowing,fire still on. When I turn thermostat to off the fan remains on and sometimes shuts off after a while and sometimes not. I've replaced thermostat twice, no change.
Submitted: 1 year ago.
Category: HVAC
Expert:  hvacexpertjoe replied 1 year ago.

Since you have already replaced the thermostat then other possible causes are that the R and W1 terminals in the furnace are touching somehow causing the heating mode to stay on. This can be caused by bare thermostat wires touching, thermostat wires pierced by metal somewhere, thermostat wires rubbing against sharp metal surface, or a micro relay on the furnace control board has welded itself in the "on" position requiring replacement of the control board. You can test this theory with a volt ohm meter. While in heating mode the "R" terminal and the "W1" terminal should be 24 volts AC to common(or C terminal). When heating is off "R" is 24 Volts AC and "W1" will be zero volts AC.

Expert:  hvacexpertjoe replied 1 year ago.

If you don't have a meter you could run thermostat and turn heat down so unit should shut off. While the unit is still heating remove the W1 wire from the furnace circuit board. If the heating stops you know the issue is with the thermostat wiring. If it continues then the circuit board is bad.

Customer: replied 1 year ago.
Thanks! It looks like a relay. Stuck closed. I'll get one and replace. Hope there's nothing else down the line.
Expert:  hvacexpertjoe replied 1 year ago.

Ok.Good luck.