Why is the fan still running after the car is turned off?
3 Answers
It is normal for the fan to continue running after the car is turned off. When the engine coolant temperature is higher than the acceptable soak temperature for the engine at the moment of parking, the vehicle's computer will automatically calculate the fan's operating speed and duration, thereby controlling the fan's operation. Below is an introduction to why the fan may still be running after the car is turned off: 1. The higher the engine temperature, the longer the fan will run after parking. When the engine coolant temperature drops below the soak temperature, the fan will turn off, protecting the engine and extending its service life. 2. The car radiator consists of three parts: the inlet chamber, the outlet chamber, and the radiator core. The coolant flows inside the radiator core, while air passes outside the radiator. The hot coolant cools down as it dissipates heat to the air, and the cold air warms up by absorbing the heat from the coolant.
I've been repairing cars for over 30 years, and this situation is very common. It's basically normal for the fan to keep running for a few minutes after turning off the engine, especially after driving on the highway or climbing hills in summer. The engine compartment temperature is high, and the cooling system will work a bit longer to protect the components. But if it runs for more than ten minutes or even continuously, you need to be alert and check three things: the coolant temperature sensor is broken and reporting false temperatures, the fan relay is stuck and can't turn off, or the thermostat is stuck and the coolant circulation is not smooth. Last year, I encountered an old Mercedes with the relay contacts burned together, and replacing the relay for 80 yuan solved the problem.
Last time my car did the same thing, and I was so scared that I immediately got out to check. Actually, short-term rotation is a protective design of the cooling system to cool down the turbocharger and cylinder block after high-temperature operation. However, be cautious if it's accompanied by the coolant temperature warning light, boiling coolant, or the air conditioning not cooling—then the problem is serious. You can initially check the temperature difference between the upper and lower radiator hoses. If the upper hose is scalding hot while the lower one is ice cold, it's likely a thermostat failure. I remember once helping a neighbor with repairs and found that the radiator gaps were clogged with poplar fluff, causing poor heat dissipation and triggering the overheating protection.
