Why is it dangerous to turn on the fan on a cold engine and how to fix the problem
Content
On old domestic cars, the operation of the engine cooling system is quite simple. However, modern cars are equipped with an electric fan and various sensors, the functioning of which is aimed at increasing the efficiency of engine cooling. Over time, these elements may malfunction, which affects the performance of the fan. Therefore, car owners have to deal with possible problems on their own or contact a specialized service.
Why does the cooling fan turn on on a cold engine?
The operation of the power unit of a car is impossible without a cooling system. If problems arise with it, the motor can overheat, which will lead to its breakdown and costly repairs. One of the main elements in this system is the cooling fan. If any signs appear that indicate a malfunction of this device, you should find and eliminate the cause. Since there can be many of them, it is worth dwelling on each of them in more detail.
Lack of fluid in the system
The search for a problem should start directly with the coolant (coolant), or, more precisely, with checking its level. If it is below normal, then the coolant sensor will work even on a cold engine, thereby turning on the fan. This is explained by the fact that a small amount of liquid heats up much faster. To fix the problem, it is necessary to check the level of antifreeze in the expansion tank and radiator, and, if necessary, bring it to normal.
The coolant level must be monitored regularly and replenished as necessary, since antifreeze can evaporate, which is especially typical for the summer period.
Sensor short circuit
If the coolant test fails, attention should be paid to the sensor itself. There are times when this element "sticks", which leads to the constant rotation of the electric fan. For diagnostics, you will need a multimeter, which measures the resistance at the sensor terminals with the engine running. If the sensor is working, then the device should show infinite resistance. When the multimeter displays some kind of resistance, it means that the contacts of the sensor are closed and it needs to be replaced with a good one.
Video: checking the fan switch on sensor
Short to ground
Spontaneous fan activation may be caused by a malfunction in the fan itself. The problem lies in the closure of its contacts to ground. As a result, the device works directly from the battery, bypassing the circuit with the sensor. To eliminate the malfunction, you need to check the reliability of the fan connections, if necessary, insulate the wires, tighten the mount. A constantly running fan can lead to the following consequences:
- short fan service life;
- battery discharge (with the ignition on and the engine off);
- spontaneous combustion of the wiring in case of overheating.
Thermostat sensor
Some modern cars are equipped with a thermostat with a sensor. This design allows the cooling system to be controlled more efficiently. However, if there is a problem with the sensor, the fan will run continuously. This behavior is explained by the fact that the signal from the thermostat to the control unit is not received. As a result, the unit goes into emergency mode. Checking the thermostat sensor is similar to the procedure for the coolant sensor.
Additional sensor
Some vehicles are also equipped with an air temperature sensor. Its main purpose is to regulate the temperature indicators of oncoming air flows. When the ambient temperature is too high, the sensor gives a signal to turn on the fan. Thus, the motor cools better. If such an element is installed on your car, then during the hot period the fan will work almost constantly, helping to cool the engine. In this case, it is not recommended to turn off the sensor, since the likelihood of overheating of the power unit increases.
Oxidation or breakage of contacts
If the car is equipped with a fan that is controlled by an electronic unit, there may be problems with the contacts themselves. Over time, they can oxidize, for example, when moisture gets in, which is accompanied by the constant rotation of the fan.
Every spring and autumn, it is recommended to clean the contacts from possible oxidation, and then cover them with a special grease.
The air conditioning system
There are machines in the design of which the air conditioner and the cooling system of the power unit are interconnected. Therefore, as a result of a blockage in the air conditioning radiator, the main radiator fan is activated. In this case, the radiator of the air conditioner needs to be flushed, and it is better to subject the devices of both systems to such a procedure.
When it is advisable to repair yourself and in service
If your car has problems with the operation of the electric fan of the cooling system, you can fix the problem in the sequence described above. Almost any repair can be done by hand. Since the main problems boil down to faulty sensors, it will not be difficult to replace them. It is enough to dismantle the faulty part and install a new one in its place. If the problem lies in bad contacts, then they can be cleaned or, in extreme cases, the connectors can be replaced. If you are not confident in your abilities, then in order to avoid new problems, it is better to contact the service.
Video: Solving the problem of a constantly running fan
To decide whether it is worth doing self-repair in case of problems with the cooling fan or asking for outside help, you can familiarize yourself with the approximate prices for a particular operation.
Table: the cost of repairing the cooling system with your own hands and in service
| Name | Approximate cost, rub. | |
| Independently | In the service | |
| Fan sensor replacement | from 150 | from 500 |
| Coolant leak check | for free | from 500 |
| Coolant level check | for free | from 500 |
| Replacing the cooling fan | from 500 | 500 – 1000 Feet |
| Minor wiring repairs | for free | 200 – 500 Feet |
| Radiator cleaning | for free | От 800 |
| Replacing the thermostat | from 350 | От 800 |
It is not normal for the cooling fan to run continuously when the engine is cold. Therefore, you should deal with the malfunction that has arisen, find and eliminate the cause of its occurrence in order to exclude the rapid wear of the device. Diagnostics consists in checking the coolant level, as well as the elements responsible for the operation of the electric fan, which every car owner can do.
