The principle of operation of the radiator fan and the causes of malfunctions (works constantly, does not work)

The combustion of fuel in the ICE cylinders is accompanied by the release of a significant amount of heat, only a part of which is used by the engine and converted into mechanical energy. The rest is uselessly lost, and special devices have to be used to neutralize its excess. These include cooling system, the ability to work in any conditions provides a cooling radiator fan.

The principle of operation of the radiator fan

Before considering this issue, let's touch on the whole, what is the water cooling system of the internal combustion engine, shown below in the figure. It will allow us to remember the principle of its work.

In cases where a cold liquid passes through the motor jacket, it takes away excess heat, while the engine cools and the water heats up. Then it passes through the radiator, where it gives off the received heat to the atmosphere, and again enters the engine.

The design of the radiator is a set of thin tubes that create a large cooling surface. The oncoming air flow, passing through it, carries away the excess heat that is stored in the liquid. In cases where there is no oncoming air flow (idling of the engine, traffic jams and other similar situations), or it is not enough to cool the water to the desired temperature, the operation of the cooling radiator fan is provided.

To do this, there is a special control circuit, the basis of which is the thermal switch of the radiator fan. It controls the temperature of the liquid. When it exceeds the set limits, the sensor is triggered, at its signal the radiator fan turns on, which creates the necessary air flow. This flow cools the heated water, and when its temperature reaches the required value, the sensor again triggers and turns off the airflow.

This is how you can describe the basic principle by which the radiator fan works - it turns on when the water temperature exceeds the set one, and turns off after it drops to the desired value.

What is fraught with if the radiator fan does not work

An internal combustion engine is a complex device, and its performance is optimal when it operates at a certain temperature. As noted above, it depends on the correct operation of the cooling system. In the case when it is not possible to withstand the desired temperature, the consequences will be rather sad - if the engine overheats, it may well jam and then, at least, it will be overhauled.

The stability of the entire system should create a fan, allowing you to reduce the temperature of the water in any conditions. But if it does not work, especially when it is hot, then you need to look for why the fan does not turn on or does not spin. Now such devices are usually electrical, and the failure of the product itself is unlikely, and a possible reason for this is often the failure of its strapping (sensor, fuse, connecting wires, etc.).

This means that when figuring out the reasons why the radiator cooling fan is constantly running or why it does not turn on or does not spin, it is necessary first of all to check the device piping.

How to check the radiator fan

As we have already established, the radiator fan should turn on when the water (antifreeze) temperature exceeds the set value. You can check this by reading the instruments on the front panel. If the fan does not turn on, then you need to check the entire signal chain.

1. Check the presence of the supply voltage coming to the product. To do this, you can use a tester or a light bulb. Lack of voltage will indicate a possible blown fuse or poor contact in the wires.
2. The health of the fan itself can be checked by applying voltage to it directly from the battery. If it spins, then everything is in order with it, and the defect must be sought in other devices. If not, and the fan does not spin, then the cause of the defect is in it. In principle, in this case, you can not stand still and move on, but you must constantly monitor the temperature of the engine. When the arrow approaches the red sector, you need to stop, open the hood and cool the engine. Two tricks will allow you to move in this case too. Keep a speed of at least sixty km / h, then the constant oncoming flow of oncoming air will cool the water passing through the radiator, and you will be able to move normally as long as you maintain speed. Another technique that allows you to partially replace a non-working fan is to use heating. Switch the stove to the maximum heating mode, in this case, part of the excess heat will go through the heater. True, in the cabin it will be like in a bath, but you can get to the nearest service station.
3. To check the sensor, it is necessary to disconnect the wires from it and close them together. If at the same time the fan turns on and spins, then the sensor itself does not work, it cannot be repaired, only replaced. However, if you leave the wires closed, then you can move on, with this option, the fan spins constantly, although it is possible that the engine temperature will be lowered, but this is better than standing still.

Radiator fan runs continuously

Partially, such a case is discussed above, the reason is the failure of the temperature sensor or the short circuit of the wires going to the fan. But if it is constantly spinning, then this may be caused by the sticking of the relay. This happens quite often, especially after the relay is triggered and the fan should turn on.
Sticking relay contacts means that they cannot open, which causes a constant supply of voltage to the contacts, as a result of which the electric motor is constantly spinning. The consequences of sticking relay contacts include the fact that the radiator fan does not turn off.

Often the thermostat can be the reason that the fan shutdown does not work.. The fact is that the sensor is located in the head of the block, it is he who determines when the fan should turn on. But the coolant can move in a large and small circle, when it moves in a small one, it does not enter the radiator for cooling. The water movement mode is determined by the thermostat.

If it is stuck in the position of water movement in a small circle, then it will continue to move, overheat, which will trigger the sensor and turn on the fan, but because water does not enter the radiator, it will not cool, and the sensor will constantly signal a high temperature. As a result, the radiator fan does not turn off. Such a case is determined simply - you need to touch the hoses going to the radiator. When the thermostat is stuck, they will be cold when the engine is overheated.

If the radiator fan does not turn off due to a stuck thermostat, then sometimes you can knock on the case to eliminate this phenomenon. Often this is enough, and the defect disappears. If everything remains unchanged, then you will have to remove the thermostat, remove all the stuffing from it and then put the device itself in place.
Another variant of the same defect would be the thermostat jamming in an intermediate position. It can also cause the radiator fan not to turn off, but this situation is much more difficult to diagnose. Such difficulties are caused by the fact that a certain amount of water enters the radiator, but it passes too little, all the water does not have time to cool, which leads to engine overheating.

All of the above is not a complete description of the possible reasons why the radiator fan does not turn off. There can be many of them, sometimes quite strange and unexpected, but in each of these manifestations of malfunctions, it is necessary to look for causes and conduct a thorough analysis.

Radiator fan turns on early

The other extreme is when the fan turns on early. In this case, you need to look again at the temperature sensor. It most likely needs to be replaced. Unless, of course, there is a correct sensor. The fact is that sensors are designed for different temperatures, they are also called summer and winter, each of them must be switched on in its own temperature range. The latter work later. And if you have been using these all the time, then it may seem to you that the fan turns on early, although it happens on time and everything works correctly.

You have to really appreciate how early everything happens. If early switching is set according to indications on the instrument cluster, then this is not an indicator. However, when such an inclusion causes concern, connect the appropriate equipment through the diagnostic channel and see the actual sensor thresholds.

Cooling the engine of the car is the most important task. If the engine is allowed to overheat, then at best it will need to be overhauled. The ability to operate the car in any conditions is ensured by the reliable operation of the cooling system, which is largely determined by the correct operation of all its components.