AC blower

If you have a four or five-speed fan motor, the typical cause of a dead motor, (when jarring it does not get it going), is tight bearings in the motor, then the thermal fuse on the resistor assembly burns open. If you find the resistor to be defective, replace the motor too.

If you have a continuously-variable fan speed controller, those use an electronic module to control motor speed. An automotive vehicle is the worst possible environment for electronics, so the engineers have planted way more than necessary on them. The motor control module is the common suspect.