Purpose and principle of operation of the cooling fan

Since the operation of an internal combustion engine is associated not only with high mechanical loads, but also with critically high temperatures. For supporting working temperature power unit, so that it does not fail due to heavy loads, each modification is equipped with a cooling system. There is air and liquid cooling. Details about the motor cooling device are described in another review.

To remove excess heat from the engine, there is a radiator in liquid cooling systems, and in some car models it is not one. A fan is installed next to this element. Consider the purpose of this part, on what principle it works, how it works, and what to do if the mechanism fails on the way.

What is a car radiator fan

When the motor is running, it generates a lot of heat. The cylinder block of a classic internal combustion engine itself is designed so that there is a cavity in its walls, which is filled with coolant (cooling jacket). The cooling system includes a water pump that runs while the crankshaft rotates. It is connected to the crankshaft through a timing belt (read more about it separately). This mechanism creates a circulation of the working fluid in the system, due to which, with its help, heat is removed from the walls of the engine.

Hot antifreeze or antifreeze goes from the engine to the radiator. This element looks like a heat exchanger with a large number of thin tubes and cooling fins to increase the contact surface. More details about the device, types and principle of operation of radiators are described here.

The radiator is only useful when the car is moving. At this time, the oncoming flow of cool air blows over the surface of the radiator, due to which heat exchange occurs. Of course, its efficiency depends on the ambient temperature, but while driving, this flow is still much cooler than the engine coolant.

The principle of operation of cooling is at the same time its disadvantage - maximum cooling is possible only when the machine is moving (cold air must penetrate the heat exchanger). In urban conditions, it is impossible to ensure a constant process due to traffic lights and frequent traffic jams in metropolitan areas. The only solution to this problem is to create forced air injection onto the radiator surface. This is exactly what the fan performs.

When the engine temperature rises, sensors are triggered and the heat exchanger is blown off. More precisely, the blades are adjusted so that the air flow is not supplied against its movement, but is sucked in. Thanks to this, the device is able to increase the airflow of the radiator even while the car is moving, and when the vehicle is at a standstill, fresh air enters the engine compartment, and the hot environment near the engine is not involved.

In older cars, the fan was rigidly attached to the crankshaft, so that it had a permanent drive. If in the summer such a process is only beneficial to the power unit, then in the winter, excessive cooling of the motor is not good. This feature of the constant operation of the device prompted engineers to develop an analogue that would work only when it was required.

Fan device and types

Despite the key importance for the cooling system, this mechanism has a fairly simple device. Regardless of the modifications, the fan design will consist of three elements:

• The casing, which is the basis of the mechanism, is installed on the radiator itself. The peculiarity of this element is that its design forces the air flow to work only in one direction - not to dissipate upon contact with the heat exchanger, but to pass through it. This design of the casing allows for more efficient cooling of the radiator;
• Impellers. Each blade is slightly offset relative to the axis, like any fan, but so that when they rotate, air is sucked in through the heat exchanger. Usually this element consists of 4 or more blades;
• Drive.

Depending on the model of the device, the drive can be of a different type. There are three main varieties:

• Mechanical;
• Hydromechanical;
• Electrical.

Let's consider each modification separately.

Mechanical drive

The mechanical drive has a simple design. In fact, this type of fan is permanently connected. Depending on the characteristics of the motor, it can be connected to the crankshaft through a pulley or through a timing belt. Starting the motor immediately leads to the operation of the impeller, a constant blowing of the heat exchanger and the power unit is performed.

The disadvantage of this type of fan is that it cools the heatsink even when not needed. For example, when warming up a cold engine, it is important that the unit reaches operating temperature, and in winter this takes longer due to too cold liquid. Any malfunction of such a mechanism can seriously affect the operation of the power unit, since part of the torque is also used on the rotating element of the fan.

Also, this arrangement does not allow increasing the speed of rotation of the blades separately from the operation of the motor. For these reasons, this modification is not used in modern vehicles.

Hydromechanical drive

The hydromechanical drive is a more advanced version, which also operates from the power unit. Only in its design there are several additional elements. In such a fan, a special clutch is used, which has a viscous or hydraulic type of operation. Despite the differences, they have the same principle of operation. In the hydraulic version, the rotation of the impeller depends on the amount of oil entering it.

The viscous clutch ensures that the fan starts and stops by changing the temperature of the silicone filler (changing its density). Since such mechanisms have a complex design, and the movement of the blades depends on the working fluid, they, like a mechanical analogue, are also extremely rarely used in modern machines.

Electric drive

The electric drive is the most reliable and at the same time the simplest option, which is used in all modern cars. In the design of such a fan, there is an electric motor that drives the impeller. This type of drive has an electrical or electromagnetic principle of operation. The second modification is more common in trucks. The electromagnetic clutch has the following structure.

The electromagnet is mounted on a hub, which is connected to the armature of the electric motor through a leaf spring, and is able to rotate. In a quiet state, the electromagnet does not work. But as soon as the coolant reaches approximately 80-85 degrees, the temperature sensor closes the magnet contacts. It creates a magnetic field, due to which it attracts the armature of the electric motor. This element enters the coil and the rotation of the blades is activated. But due to the complexity in the design, such a scheme is not used in light vehicles.

The use of electronics makes it possible to provide several modes of operation of the device, depending on the temperature of the coolant and the speed of the crankshaft. The peculiarity of such a drive is that it can be turned on independently of the operation of the internal combustion engine. For example, while the engine is warming up, the fan does not work, and when the coolant reaches its peak temperature, the impeller begins to rotate.

In order to provide the cooling system with an additional air flow, in the latter case, it is enough to screw the fan into the appropriate place and connect it to the car's wiring harness. Since such a modification is used in modern vehicles, further we will consider the principle of operation of this particular type of fans.

The principle of operation of the engine cooling fan

To activate the fan when needed, it is connected to another system that monitors the working environment. Its device, depending on the modification, includes a coolant temperature sensor and a fan relay. This electrical circuit is connected to the fan motor.

Such a simple system works as follows. A sensor installed at the radiator inlet records the coolant temperature. As soon as it rises to the appropriate value, the device sends an electrical signal to the relay. At this moment, the electromagnetic contact is triggered and the electric motor is turned on. When the temperature in the line drops, the signal from the sensor stops coming, and the relay contact opens - the impeller stops rotating.

In more advanced systems, two temperature sensors are installed. One stands at the coolant inlet to the radiator, and the other at the outlet. In this case, the fan is turned on by the control unit itself, which determines this moment by the difference in indicators between these sensors. In addition to this parameter, the microprocessor takes into account the force of pressing the gas pedal (or opening choke), engine speed and readings of other sensors.

Some vehicles use two fans to improve the performance of the cooling system. The presence of an additional rotating element allows for faster cooling of the heat exchanger due to the greater flow of cool air. The control of such a system is also carried out by the control unit. In this case, more algorithms are triggered in the microprocessor. Thanks to this, the electronics can not only change the speed of rotation of the blades, but also turn off one of the fans or both.

Also, many cars are equipped with a system in which the fan continues to work for some time after the engine is turned off. This is necessary so that after intensive work the hot motor continues to cool down for some time. When the engine is turned off, the coolant stops circulating through the system, due to which the temperature in the unit rises sharply, and heat exchange is not performed.

This happens extremely rarely, but if the engine was running at maximum temperature and was turned off, the antifreeze can begin to boil and form an air lock. To avoid this load in some machines, the fan continues to blow air to the cylinder block. This process is called fan free run.

The main malfunctions of the radiator fan

Despite the simple design and high reliability, the cooling fans also fail, like any other mechanism in the car. There may be many different reasons for this. Let's consider the most common breakdowns and how to fix them.

Most often, drivers are faced with the following malfunctions:

• When the engine is running (the car is standing for a long time), the forced blowing of the heat exchanger does not turn on;
• The fan operates at higher temperatures;
• The air is blown onto the radiator constantly;
• The blades begin to rotate much earlier than the coolant reaches the required heating;
• The fan turns on too often, but the motor overheat light does not work. In this case, you should check how dirty the radiator cells are, since air should not just flow to the surface of the heat exchanger, but pass through it;
• When the radiator airflow is turned on, the flow does not go into the engine compartment, but is fed in the opposite direction. The reason for this work is the wrong pinout of the cables (you need to swap the poles of the electric motor);
• Breakage or deformation of the blade. Before replacing the impeller with a new one, it is necessary to find out the cause of such a breakdown. Sometimes this can happen with an illiterate installation or installation of a fan that is not intended for this car model. Otherwise, the breakage of the blades is a consequence of the natural wear of the material.

While all of these "symptoms" are undesirable for proper operation of the power unit, it is worst if the fan does not turn on at all. This is so, because in this case, overheating of the motor is ensured. If you continue to operate it at elevated temperatures, it will quickly fail.

If the fan operates at a temperature exceeding 80-85 degrees (most often this happens after replacing the temperature sensor), you should check whether the coolant temperature sensor is selected correctly. There are modifications for vehicles operating in northern latitudes. In this case, the device is set to operate at higher temperatures.

A faulty thermostat can also cause overheating. Details about this device tells here... In this case, one side of the cooling system will be excessively hot and the other cold.

The reason for the breakdown of the forced cooling system (not related to the thermostat) may be the failure of one of the sensors (if there are several) of the coolant temperature, the breakdown of the motor motor, or the loss of contact in the electrical circuit (for example, a wire core breaks down, insulation is damaged or contact is oxidized). First, you need to conduct a visual inspection of the wiring and contacts.

Separately, it is worth mentioning the infrequent problem of a working fan with a cold engine. This problem is typical for vehicles equipped with interior air conditioning.

Details about her are described in this video:

FAN RUNNING on COLD ENGINE. WHAT TO DO. For all machines with AIR CONDITIONING.

Also, the system can be tested in the following ways:

1. "Ring" the wiring using a tester, multimeter or "control";
2. The electric motor can be tested for operability by connecting it directly to the battery. In this case, it is important to observe the polarity. If the engine works, then the problem is in the wires, poor contact, or in the temperature sensor;
3. The serviceability of the sensor is checked by closing its wires. If the fan turns on at the same time, then the temperature sensor needs to be replaced.

It is worth considering that for many latest car models, such diagnostics are not available due to the fact that the wiring in them can be well hidden, and it is not always easy to get to the sensor. But if there is a problem with the fan or one of the system components, the electronic control unit will immediately generate an error. In most cases, the engine icon will light up on the instrument panel. Some on-board systems allow standard self-diagnostics. How you can call up the corresponding menu on the on-board computer screen, read here... Otherwise, you need to go to computer diagnostics.

As for the early operation of the fan, this is often a symptom of a faulty coolant temperature sensor. Although every auto mechanic cannot subscribe to this conclusion, if the engine normally reaches operating temperature, then you should not worry that the system turns on earlier than necessary. Overheating is much worse for the internal combustion engine. But if it is important for the driver that the car meets environmental standards, then this problem must be solved, since in a cold engine the air-fuel mixture does not burn so efficiently. Over time, this will negatively affect the catalyst (for why you need it in the car, read here).

If the fan motor runs constantly, this is a symptom of a failed sensor, but more often this happens due to "stuck together" contacts in the relay (or the coil of the electromagnetic element burned out, if this modification is used in the machine). If the thermostat breaks, then often the radiator will be cold and the fan will not work, even at a critical motor temperature. This happens when the thermostat is stuck in the closed position. If it is blocked in the open state, then the cold internal combustion engine will take too long to reach the operating temperature (the coolant immediately circulates in a large circle, and the engine does not heat up).

What to do if the fan fails while traveling?

It is not uncommon for a cooling fan to break down somewhere on the road. If it stops working, then in city mode the antifreeze will surely boil. Here are a couple of tricks that can help in this case:

• Firstly, if a breakdown occurred on the highway, then in high-speed mode it is easier to provide airflow to the heat exchanger. To do this, it is enough to move at a speed not lower than 60 km / h. In this case, cool air in large quantities will flow to the radiator. In principle, the fan rarely turns on in this mode, so the system will operate normally.
• Secondly, the heating system of the passenger compartment uses the thermal energy of the cooling system, therefore, in emergency mode, you can turn on the heating in order to activate the heater radiator. Of course, in the summer, driving with the interior heating turned on is still a pleasure, but the engine will not fail.
• Thirdly, you can move in short "dashes". Before the coolant temperature arrow reaches its maximum value, we stop, turn off the engine, open the hood and wait until it cools down a little. In no case, during this procedure, do not water the unit with cold water, so as not to get a crack in the cylinder block or head. Of course, in this mode, the journey will be significantly delayed, but the car will be intact.

However, before performing such procedures, you should check why the fan does not turn on. If the problem is in the wiring or sensor, then to save time, you can connect the electric motor directly to the battery. Don't worry about running out of battery. If the generator is working properly, then while the internal combustion engine is working, the on-board system is powered by it. Read more about the generator's operation. separately.

Although in many cars you can replace the air blower yourself, if the car is still under warranty, it is better to use the services of a service center.

Questions and answers:

What is the name of the fan on the engine? The radiator fan is also called a cooler. Some vehicles are equipped with a double cooler (two independent fans).

When should the car fan turn on? It usually turns on when the car is standing for a long time or is in a jam. The cooler turns on when the coolant temperature exceeds the operating indicator.

How does a car fan work? During operation, the motor gains temperature. To prevent it from overheating, a sensor is triggered, which activates the fan drive. Depending on the car model, the fan works in different modes.

How does the fan cool the engine? When the cooler is turned on, its blades either suck in cool air through the heat exchanger or pump it onto the radiator. This speeds up the heat transfer process and the antifreeze is cooled.