Air conditioners and heaters accomplish their tasks unnoticed when working properly. But as soon as they stop working, it's readily apparent. The freezing air makes you shiver, or the summer heat makes you sweat. When this happens, your main concern is to get them running again as soon as possible. Before calling in a service technician, there are troubleshooting methods you can try to get your unit up and running without a costly service call.
Check the circuit breaker for your AC or heater unit and inspect the fuses. Turn any breaker that is in the "Off" position to the "On" position. Unscrew and replace any fuses that are blown.
Turn the power button next to the AC/heating unit to the "On" position.
Check the thermostat. Set it to turn on the AC or heat. Walk to the AC/heating unit and listen for the motor to turn on. If it doesn't, there could be something wrong with the thermostat.
Remove the cover for the thermostat and unscrew the wire from the Y terminal (it should be marked). Hold the wire by the insulation and touch the bare end of the Y wire to the R terminal to bypass the thermostat. Hold it for two minutes. If the motor turns on, the thermostat is faulty and needs to be replaced.