- Faulty fan control module: This module controls the fan speed based on the temperature reading it gets from the radiator temperature sensor. If the fan control module is defective, it may not send the correct signal to the fan, causing it to not come on.
- Broken or disconnected wiring: Check the wiring that goes from the radiator temperature sensor, fan control module, and fan. Make sure the wires are not broken, loose, or corroded.
- Faulty fan: The fan itself may have a problem causing it not to come on. To check this, you can try connecting the fan directly to a 12-volt power source. If the fan does not come on, it is faulty and needs to be replaced.