Fan switch sensor: common defects and their signs

1. Terminals oxidation.
   • The fan doesn’t switch on when the cooling liquid reaches the critical temperature.
   • The engine overheats.
   • The fan turns on earlier than cooling liquid temperature reaches a critical point.
2. Body deformation.
   • The fan is running constantly, regardless of cooling liquid temperature.
   • Antifreeze boiling occurs.
   • The fan turns on but runs erratically.

How to replace fan switch sensor?

Specialists recommend to check the car fan switch sensor every 25,000 kilometers of mileage. The part can not be repaired, and should be immediately replaced at appearance of defect signs. Buying a component for a car, make sure that the response temperature of new fan switch sensor is equal to the same parameter of the broken down component.

The procedure for part replacement depends on its mounting location. If the sensor is mounted in the cooling liquid connecting pipe, it can be replaced on your own. Before starting works, study technical documentation, as the replacement algorithm may vary for different car models. Basically, the replacement algorithm is as follows:

1. After the engine cools down, disconnect the wire from the negative terminal of the battery.
2. Disconnect terminals from the fan switch sensor and remove it.
3. Treat a new component thread with a thin layer of sealing compound, or cover it with teflon ribbon, in order to prevent cooling liquid leakage.
4. Install a new gasket under a new sensor and screw the latter, avoiding excessive tightening.
5. Reassemble in the reversed order.

If the fan switch sensor is mounted in the radiator or on the cylinder head, near the thermostat, the replacement process will be more laborious. It is recommended to entrust this procedure to service station specialists.