There could be several reasons why your heater fan is not working:
Blown fuse: Check the fuse box for any blown fuses related to the heater fan. If you find one, replace it and try again.
Faulty fan motor: The fan motor may have failed, which means it won't be able to spin and blow air through the vents. You can check this by turning the fan on and listening for any noise coming from the motor.
Broken resistor: The resistor is responsible for regulating the fan speed. If it's broken, the fan may not work at all or only work on one speed.
Bad relay: The fan relay controls the power to the fan motor. If it's not functioning properly, the fan may not work at all.
Wiring issues: There could be a problem with the wiring that's preventing power from getting to the fan motor.
