Cause 1
On - Off Switch
To determine if the switch is defective, use a multimeter to test it for continuity. If the on-off switch does not have continuity, replace it.
Cause 2
Drive Motor
First, test the power switch for continuity to ensure that the motor is getting power. If the power switch has continuity, ensure that the blower wheel turns freely and is clear of obstructions. If power is getting to the motor, and the motor turns freely, but the motor still won’t run, replace the motor.
Cause 3
Fan Motor
First, test the power switch for continuity to ensure that the motor is getting power. If the power switch has continuity, ensure that the blower wheel turns freely and is clear of obstructions. If power is getting to the motor, and the motor turns freely, but the motor still won’t run, replace the fan motor.