Incorrect low voltage wiring, or if the wiring is old, most likely a break in the insulation of the wiring creating a short. First thing, check the wiring diagram to see that all wire colors are attached where they should be at the thermostat. Then look at the wiring diagram at the air handler and verify the control wires are on the proper terminals.
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Incorrect low voltage wiring, or if the wiring is old, most likely a break in the insulation of the wiring creating a short.
First thing, check the wiring diagram to see that all wire colors are attached where they should be at the thermostat.
Then look at the wiring diagram at the air handler and verify the control wires are on the proper terminals.