My aux heat indicator light comes on in air conditioner mode, what should I do?

Answer by  kipcat (1964)

The aux-heat light should only come on when the card in the condensing unit senses a temperature below about 35 degrees. Your problem might be an outdoor air temperature sensor.

Answer by  AbbieThompson (175)

There could be one of two things wrong. If the light has been coming on since the unit was installed, the wiring on the computer board in either the unit or the thermostat could be wrong. If the light just started coming on, the thermostat more than likely needs to be replaced.