Why does the engine cooling fan often turn on
Unlike a household fan that operates on hot days in apartments and offices, a car fan is not the main, but only an auxiliary mechanism of the cooling system. The main role in water systems (and the vast majority of cars today are equipped with such systems) is still played by the coolant - antifreeze, and the state of the circuit in which it is located. The fan, as a rule, is connected only when other components (thermostat, radiator) are not able to cope with engine cooling.
FAN OPERATING PRINCIPLE
The fan is always located in close proximity to the main radiator of the cooling system. Electric fans are placed in a casing screwed to the radiator housing, mechanical ones are located between it and the cylinder block.
Depending on the design, the cooling fan drive is implemented according to the following schemes:
Mechanical. The blades are either mounted on the crankshaft pulley or have a permanent belt drive. The most reliable, but outdated scheme, is used today mainly on special equipment or heavy trucks (although cars were also equipped with it in the past). A significant disadvantage is the constant cooling of the engine, leading to insufficient warming up at low temperatures.
Viscous coupling. Further development of the mechanical scheme. The base part of the fan has a permanent belt drive, and the blades are connected through special bimetallic plates, when heated, both parts are connected by a viscous gel that transmits rotation like an automatic transmission torque converter. The main disadvantages are the low accuracy of temperature control and the complexity of the design. Currently not applicable.
From the coolant temperature sensor located in the radiator. The first version of the electrical circuit for connecting the fan. It was used in carbureted cars and the first generations of injection cars. The main drawback is the irrelevance of temperature control, especially in the event of damage and subsequent emptying of the radiator.
From the ECU, engine control unit. The most accurate and adequate method used in modern cars. On most machines, the ECU receives data from several sensors located in different parts of the engine, and based on their readings, it supplies current to the fan motor. The cooling system heats up gradually. First, a small circuit is heated: the engine cooling jacket and pipes going to the passenger compartment and to some attachments. Upon reaching a temperature close to the operating temperature in this circuit, the thermostat opens the way for liquid to a large circuit: the radiator and its pipes. Radiator cells, in contact with atmospheric air, give it heat. When natural airflow becomes insufficient, a forced one is connected using a fan. Modern cars are equipped mainly with two (often identical and interchangeable) cooling fans. But this does not always mean the possibility of dual cooling: most often one fan is responsible for the cooling system, and the other for the air conditioner, the radiator of which (condenser) is located in front of the main radiator. This fan turns on when the freon needs to be cooled down.
CAUSES OF THE FAN TURNING ON TOO FREQUENTLY
Cars of recent years of production are mainly equipped with electric fans that do not work constantly, but turn on at the moment when the cooling system needs their help in lowering the temperature of the antifreeze and, as a result, the engine. Problems with such fans are divided into two groups:
airflow does not turn on when the engine is heated;
The fan does not turn off or runs very frequently.
The first case is most often caused by a failure of the electrical part: problems with the sensor or its circuit, a blown fuse, less often - a malfunction of the fan itself, its electric motor, or jamming of the blades as a result of mechanical impact (for example, after a small accident, when the radiator housing has shifted, but it does not lost seal).
Frequent turning on of the cooling fan is usually not the fault of the fan switching system and accompanies other symptoms of overheating in the car. This can be caused by problems in other nodes:
Thermostat. The device that regulates the passage of fluid through the cooling system can jam either in the closed position (then the coolant will circulate in the inner circle without entering the radiator), or in the half-closed position - the movement of antifreeze in this case will slow down and the heat sink will worsen. The engine will start to overheat faster, respectively, the fan will turn on more often.
Water pump (pump). Insufficiently efficient operation of the pump also contributes to a decrease in the rate of circulation of the coolant, as a result - overheating of the engine. In addition to problems with frequent turning on of the fan, this is also a very serious symptom - as a rule, in this way the pump gives signs that precede its imminent final breakdown.
Radiator. Dust and dirt flying from the road clog the space between the radiator cells, which leads to poor cooling of the antifreeze and overheating of the system. In this case, it is necessary to clean the radiator, preferably with its dismantling.
Clogged channels in the cooling system. If all of the above systems are operating normally, and the fan still turns on too often, the ducts may be dirty. It is necessary to change the antifreeze and be sure to flush the system.
Air locks in the cooling system. They can form when the coolant is incorrectly replaced, as well as due to leaks in the system. In the presence of air, antifreeze heating
is uneven, which leads to unstable operation of the fan.
Frequent turning on of the fan in the heat - at an air temperature of +25 ° C and above, at a particularly low speed, as well as when the air conditioner is turned on - is a regular phenomenon that is not a malfunction. However, the driver must still monitor the readings of the instruments, primarily the temperature gauge, preventing it from moving into the emergency (red) zone).
WHAT TO DO IN THE EVENT OF A FAULTY
It is impossible to operate a car in which the cooling fan turns on too often, even if the temperature readings do not reach critical values. The situation may be the result of local overheating outside the area of responsibility of the temperature sensors. Problems need to be identified and resolved as soon as possible.
If the frequent turning on of the fan is caught on the way, you need to take measures to allow the engine to cool normally:
move at low speeds, but at a fairly high speed (if possible, from 60 km / h), in direct or overdrive;
turn on the heater, the radiator of which will also take heat from the system, and the air conditioner - its fan will help the main one;
if available, monitor the temperature readings using a scanner;
when the temperature rises critically, stop, but do not immediately turn off the engine, let it run at idle. Do not open the radiator or expansion tank cap in any case - this can lead to splashing of antifreeze and burns. It is also not recommended to open the hood in hot weather - this will not help cool the engine.