Honeywell Thermostat Fan Runs Constantly. The fan will run until the air reaches the temperature set on your thermostat, then the system stops running and automatically turns the fan off. When the thermostat is set to fan on it may sound like the heating or cooling is running even when it isn’t.
Your a/c or heater runs constantly and won't turn off. The first thing to do to solve the honeywell thermostat troubleshooting is by testing the heat. Fan should not run constantly independently of compressor unless in on vs auto mode.