- The blower motor resistor may be faulty. This resistor controls the speed of the fan, and if it fails, the fan will only run at high speed.
- The blower motor itself may be faulty. If the motor is damaged, it may only be able to run at high speed.
- The climate control module may be faulty. This module controls the operation of the heater and air conditioning system, and if it fails, it can cause the fan to only run at high speed.
To diagnose the problem, you will need to test the blower motor resistor, the blower motor, and the climate control module. You can do this yourself if you have the necessary tools and knowledge, or you can take your vehicle to a qualified mechanic.
Once you have diagnosed the problem, you can then replace the faulty part and restore the fan to normal operation.
