Propeller or car fan
During engine cooling, the fan system is responsible for supplying the air required for the process of reducing the water temperature in the radiator. We usually see the car fan in the form of a fan in front of the engine. For this reason, car fan is also called engine fan or radiator fan. This propeller, which is responsible for the blower of the cooling system, is used in two general ways in cars.

mechanical fan
Of course, the use of mechanical fans is obsolete nowadays and we only see electric fans. Electric fans with their components are placed in the electrical part of the cooling system.

electric fan
The system of these fans, which can be seen in all cars today, consists of a propeller with an electric motor. This engine supplies the necessary energy for the operation of the car’s propeller. The electric motor of this system also receives its required electricity from the battery. In this way, it is possible to activate this fan in any condition and at desired speed. The components of the fan set include the following:

Propeller, electric motor, control relays, ECU, water sensor in injection cars, water temperature gauge in carburetor cars
The ECU in the car’s electric fan system may be separate and dedicated to it, or a common unit with the fuel system may be used for it. Sensors are also thermistors whose electrical resistance changes with changes in water temperature. This change in resistance is sent to the ECU as monitorable signals and the unit obtains the necessary information to control the operation of the fan. In this way, the ECU determines whether the fan is fast, slow or off by checking the information of the water temperature sensors and sends the relevant signals to the fan electromotor through the control relays.

The types of fans are as follows:

Clutch fan:
This type of fan is a mechanical type that is activated with the help of a propeller belt. In the clutch fan, which is usually used in SUVs and pickup trucks, the propeller and its axis, which is rotated by the belt and the motor, are separate from each other. Therefore, the rotation of the belt does not necessarily drive the car’s fan. In the meantime, what causes the fan to work is the clutch that exists between them, and it engages with the increase in heat and causes the rotation force to be transferred to the machine’s propeller.

Plastic fan:
This lightweight fan whose blades have angled edges is able to direct more wind towards the radiator due to the characteristics of its blades. The important thing about this type of fan is the flexibility of its blades. In this way, its blades change shape at high speeds and control the blowing of the wind by reducing its angle.

Aluminum fan:
This fan, which has a light weight like the plastic type, does not have the ability to change the angle of the blade and generally does not have an angled blade.

Steel fan:
This type of fan, which is similar in design to the aluminum type, weighs more than it, and for this reason, its use is obsolete today.

In the investigations, the efficiency of the motor with a clutch fan is more than other types, and the steel fan also results in the most energy wastage. But even the clutch fan takes about 14 horsepower from the engine. This was one of the main reasons for replacing these fans with electric ones.