Everything You Should Know About Electric Cooling Fans of Motor Vehicles

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An electric cooling fan of a motor vehicle is made up of (1) the fan motor and (2) the circuit. The circuit consists of the fan switch and the relay. The function of the switch is to send power to the relay and to sense the internal temperature of the engine and switch on the cooling, if there are signs of heating.

Generally the electric cooling fan is mounted behind the radiator. However in some vehicles, there may be large and wide radiators. In such cases, there may be two fans, or there may be a separate fan purely for the air conditioning condenser.

Mostly the fans are switched on when there is heating inside. This helps to cool the engine. There is a separate engine temperature switch or an engine coolant sensor which is used to monitor the engine temperature. When the engine is first started, the fan is not started until it reaches the normal operating temperature which is between 195 to 215 degrees. Then the fan will cycle on and off as needed to maintain the temperature. So if the engine is at normal temperature, the fan will run in a low or idle speed.


The main reason why electric cooling fans are now used in many vehicles in place of the traditional belt driven mechanical fan is to improve the fuel consumption and reduce the noise of the fan, especially when the vehicle is running at high speed. A fan that is driven by a belt can consume more than 12 horsepower or even more depending of course of the speed of the engine and the load.

The engine can become overheated if the fan fails to function properly or there is a failure of the fan relay or control circuit.

Some of the main reasons for failure of the fans to function properly are:

The temperature switch may be defective or the coolant sensor engine thermostat is stuck open as a result of which the engine never gets hot enough to turn on the fan.
There is a failed fan relay
There are some wiring problems or blown fuse, loose or corroded connector, shorts, opens, etc.
Defective fan motor

The easiest way to know whether the electric cooling fan is working properly or not is to start the engine and let it reach the normal operating temperature and then turn the car AC on. When this is done, the cooling fan inside the engine compartment should turn on to pull the air through the radiator and the condenser of the AC. There are some vehicles which are fitted with two fans, one is the main cooling fan for the radiator and the other fan is for the condenser. Both the fans should come on when the AC is switched on.


If there is a defective fan or both the fans fail to come, there will be no cooling of the engine. This will cause the AC to function poorly, or it may cause the compressor of the AC to become overheated and ultimately fail. Eventually the engine will become overheated very soon.

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