Likely cause: Fuse or circuit breaker is tripped. What to do: Replace the fuse or reset the breaker. Likely cause: Armature is shorted. Motor may make a humming noise and the circuit breaker or fuse will trip. What to do: Disassemble motor and inspect the armature for a burnt coil. Inspect the commutator for burnt bars. If this condition exists, the motor needs to be replaced. Likely cause: The brushes may be worn down too far and no longer make contact with the commutator. What to do: Check the brushes to make sure that they are still making contact with the commutator. Contact manufacturer for brushes. Likely cause: Controller may be defective. What to do: Verify voltage is coming out of the controller.