Hi: You need to start at the motor and work back. Check for power to the motor. If power and the motor doesn't run, replace the motor. If no power, move to the blowermotor resister. If power in but not out, replace resister (most common problem). If no power in, move to the switch and see if there is power both in and out. If power in and not out, replace the switch. If no power in, you will need to follow the power supply back to determine where it's lost.