Common Radiator Fan Failures

There are many common reasons for failure. The first reason is that the electronic fan does not rotate or the speed is abnormal.

 Common faults:
1. The electronic fan does not rotate or the speed is abnormal   

   The first problem of fan motor failure is of course the problem of the radiator fan itself. The most common problem is that the fan motor is damaged, causing the radiator fan to fail to operate.

2. Water temperature sensor plug failure
For models where the radiator fan is controlled by the engine control unit, during engine operation, the engine control unit controls the operation of the radiator fan based on the data from the water temperature sensor. Usually, when the water temperature sensor measures a water temperature of about 95°C, the control unit turns on the low speed gear of the fan, and turns off the fan when it is lower than this value. When the water temperature reaches about 105°C, the control unit turns on the high speed gear of the fan, and switches to the low speed gear when it is lower than this value. Therefore, if the water temperature sensor fails, the control system cannot obtain the correct water temperature signal, causing the fan to not work properly.

Mercedes Benz 274 920 205

3. Thermal switch failure

  When the radiator fan is controlled by a thermal switch and a fan high-speed relay. The thermal switch is installed on the radiator. When it detects that the water temperature reaches about 95°C, the switch is turned on and the fan starts at low speed. When it detects that the water temperature reaches about 105°C, the fan high-speed relay contacts are closed and the fan starts at high speed. Therefore, when there is a problem with the thermal switch, the radiator fan cannot work normally.

4. Fan controller failure

This also applies to models where the radiator fan is controlled by a thermal switch and a fan high-speed relay. When the high-speed relay fails, it will cause fan problems. For example, if the contacts of the high-speed relay cannot be closed, the radiator fan will only run at low speed but not at high speed. If the contacts of the high-speed relay are always closed, the fan will always run at high speed.

Piston Mitsubishi  4G69 69SA   MN163080