How to Diagnose an AC's Electric Motor

Unplug your air conditioner from its power source. Remove the holding screws that fasten the metal cover to the air conditioner frame, then remove the metal covering to see the electric motor.

Smell the electric motor, but do not place your face too close to the motor. A strong burned odor is indicative of burned magnetic wires which causes an open circuit. An open, or disconnected circuit will cause the electromagnet inside the motor to stop working.

Look at the fan attached to the motor. Turn the fan blades clockwise to see if the fan will spin freely and easily. Fan blades on a working air conditioner electric motor will easily rotate a few rounds when pushed manually. A fan that is hard to move or that is stuck is indicative of damaged bearings, or bushings that hold the motor spindle in place.

Plug the air conditioner to a power source, then turn on the appliance. Observe the fan and listen to the sound produced once you turn on the air conditioner. If the motor hums, but does not turn, spin the fan blades with a stick to make them rotate. If the motor spins only when pushed each time the appliance is turned on, then there is a high probability that the starting capacitor is defective.

Inspect the wires running into the electric motor and check for any sign of burned, or damaged wiring. Shorted wires can cause the fuse to blow and cut the flow of electricity to the motor.