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Fan thermo-switch/sensor replacement

Fan thermo-switch/sensor replacement

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The fan sensor, also called thermal switch, is responsible for turning on the engine fan in the right moment, i.e. when the coolant temperature exceeds a predetermined value. When worn, the sensor requires replacing. In the event of a failure, the fan may operate continually, irrespective of the engine temperature, or stop operating at all, even after the critical temperature is exceeded, resulting in engine overheating.

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service info

Tips

  • Have the coolant changed each time you have the fan sensor replaced
  • Sensors differ in terms of their parameters - it is very important to make sure that you choose one that fits your engine version
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Range of services

  • Releasing the coolant from the system
  • Disconnecting the electrical cables
  • Replacing the sensor with a new one and connecting it to the system
  • Refilling the system with fresh coolant
  • Checking if the fan is activated when the temperature is right

Car workshops: Fan thermo-switch/sensor replacement

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    Service description

    What is the role of the radiator?

    The radiator is one of the most important elements of the engine cooling system. Hot coolant flows through it to be cooled by the air flowing around it while the car is moving. This way, excess heat is removed from the engine. When the car is stationary, the necessary air flow is provided by the electric fan.

    What is the role of the thermal sensor?

    To prevent the fan from working continually and from cooling the engine when not required to do so, e.g. in winter, the cooling system is equipped with a fan thermal sensor. After the coolant reaches the critical temperature, the sensor causes the electrical circuit to close and, consequently, the fan engine switches off.

    How is the fan thermal sensor changed?

    Like any other electrical device, the thermal sensor may brake down. If this is the case, the fan may work continually, irrespective of the coolant's temperature, or worse, it may not switch on at all, even if the engine temperature goes beyond the limit. In such case, the thermal sensor must be replaced by means of removing it from the element of the cooling system in which it is fitted, usually the engine head or a radiator hose.

    What to keep in mind

    As removing the switch requires opening the cooling system, it should be cleared off the coolant beforehand. Next, after disconnecting the electrical plug, the faulty sensor is replaced with a new one. After reconnecting the electrical system, the coolant is refilled to the required level and the engine is turned on to check if the radiator fan operates properly. It is also possible to check if the vent switch works properly by means of connecting it to a diagnostic tester.