The function of engine cooling fan is to enhance the air flow rate and flow rate through the radiator to improve the heat dissipation effect. As an important part of the engine cooling system, the work of the fan not only directly affects the heat dissipation efficiency of the radiator, but also affects the normal use and reliability of the engine.

Many parts of a car need to dissipate heat when running, so there are many places inside the car need to install fans, including clutch fans, electric fans, and ordinary ordinary cooling fans.

1. Clutch fan

The clutch fan is equipped with a fan clutch between the belt pulley and the hub of the fan blade. This not only ensures the normal operating temperature of the engine, but also reduces the power loss and fuel consumption of the engine. Common clutch fan has electromagnetic clutch fan and silicon oil clutch fan. The electromagnetic fan clutch, when the coolant temperature reaches the specified value, the coolant temperature sensor switch or air temperature sensor switch automatically switch on the circuit, the clutch coil is energized to form a closed magnetic circuit to generate magnetic tension, so that the armature and pulley joint, fan work; When the coolant temperature drops, the sensor switch is disconnected, the armature is quickly reset under the action of the diaphragm spring, the clutch is separated, and the fan stops working. The silicon oil clutch fan is in a closed state when the engine temperature is high. The fan works to reduce the temperature of the radiator. When the engine temperature is low, the fan clutch automatically disengages and the fan does not turn, saving engine power and raising the cooling water temperature. Fan rotation does not indicate whether the fan clutch is malfunctioning, because both the malfunctioning and normal fan clutch will follow the pump belt pulley when it is in the state of disengagement. You can tell if the fan clutch is working by listening to the sound of the fan. A normal fan clutch makes a sound that works normally when the engine's water temperature is higher than 86 ° c, while a malfunctioning fan clutch makes a much quieter sound. When the fan clutch fails, when the engine water temperature is high, the fan does not turn, then it is necessary to turn off the engine, loosen the nut, insert the locking plate into the pin hole of the drive shaft, so that the fan and the drive shaft are fixed, do not use the fan clutch, so that the fan is forced to turn; When there is an opportunity to repair the fan clutch, then restore the fan clutch automatic clutch function.

2. Ordinary cooling fan

The fan is located between the radiator and the body, mounted on the same shaft as the water pump, and driven by a pulley on the crankshaft. The fan is connected with the belt wheel hub with bolts, and the belt wheel of engine crankshaft drives the fan to rotate directly or indirectly.

The tightness of each belt should be adjusted according to regulations. Fan belt tight through loose, causing the fan pulley speed is reduced, the tank heat dissipating capacity is abate, make diesel engine work temperature, at the same time reduce the generator output current or unstable, but the fan belt tightness is not the bigger the better, fan belt too tight will make bearing load is too big, wear, power consumption increases, at the same time also can make water pump shaft bending, belt stretching deformation, shorten service life. Therefore, the fan belt should be kept properly tight and adjusted when necessary. Check the tightness of the belt method: with finger or ruler with 30 ~ 50N pressure in the middle of the belt, belt down 10 ~ 20mm is appropriate. Some engines have two belts, others three or four. Each belt gear shall be on the same plane and shall not be twisted when installed. If the belt is seriously worn or broken, it should be replaced in time. If the fan belt is two, the replacement must be replaced at the same time, so as to avoid its tension, uneven force, causing fault.

3. Electrically controlled fan

Electric fan working principle, this kind of fan is driven by its own fan motor. The motor's circuit switch is controlled by a fan sensor (temperature control switch) mounted in the radiator launching chamber. When the radiator water temperature is above 86-90 ℃, the temperature control switch is connected to the fan motor circuit, making the fan rotate to accelerate the radiator cooling. When the radiator water temperature drops to below 81-85 ℃, the fan sensor is disconnected, the fan motor circuit is broken, and the fan stops rotating.