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Heating, Air Conditioning, Fridge, HVAC/Heat Pump System just stopped working


What would cause the thermostat to lose power (backlight went off) and will not respond (numbers display though?) Read online to use a jumper to test for a bad thermostat (R to G) and that did not start the fan. It's an electric heat pump system with an attic air handler (cannot easily access, so I have not went up there.) I checked all the breakers and all is well. I reset the outside breaker. It was working just fine and all of sudden it just stopped. Any ideas?

110/120 volt power goes from the breaker panel to the unit in the attic, the attic unit has a 24 volt transformer that sends 24 volts of power to the thermostat, the "R' post/connection in the thermostat is where 24 volts of power connects, when you set the thermostat to heat the "R" post power feeds the "W" post which feeds the power to the heat controls, take the wires loose from the R and the W posts and lightly flick/touch them together, you should get a spark, 24 volts won't shock you unless your standing barefoot in some water!
If you twist the R and W wires together you should get heat?
If you don't get heat or a spark the thermostat isn't getting power?

Heating, Air Conditioning, Fridge, HVAC

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Jim Barnhart


Fifty + years conditioning the air.


Answer questions about , residential and commercial. Answer questions about sheet metal fabrication. Fifty years plus experience. No answers for oil equipment, No answers for kitchen appliances, No answers for laundry appliances, I don't specialize in one particular area of the HVAC area, I'm more of a General Practitioner, Limited in refrigeration/

Hands on since 1950

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