Why does the fan keep running after the car key is pulled out?
3 Answers
It is normal for the fan to keep running after the car key is pulled out, and there is no need to worry. It usually stops after a few minutes. The fan is the cooling fan, whose main function is to blow air for cooling. This means that as long as the temperature is high, the fan will operate. There is a sensor on the side of the engine compartment. When the engine temperature is higher than the set value, the fan will start working. When the engine temperature drops below the set value, the fan will automatically stop. Pulling out the key only cuts off the power to the vehicle's electrical appliances, but it does not mean that all the circuits in the car are powered off. For example, the car's anti-theft device is directly connected to the car battery. The fan is not controlled by the key; the cooling fan is directly connected to the battery. Therefore, as long as the battery has power and the engine temperature is high, the fan will continue to run until the temperature drops.
I've encountered the situation where the fan keeps running after pulling out the key several times while driving, and it was quite nerve-wracking at first, worrying that something might be wrong with the car. Actually, this is quite normal most of the time, especially after driving on the highway or during hot weather when the engine accumulates a lot of heat. The fan needs to keep running for a few more minutes to dissipate the heat and prevent internal components from overheating and getting damaged. The car's temperature controller monitors the situation and will automatically stop the fan when everything is normal. However, if the fan keeps running for an unusually long time without stopping, or continues to run even when the car has cooled down, there might be a problem, such as a faulty temperature switch, a stuck relay, or a short circuit in the wiring. I recommend calmly observing for a few minutes first. If it exceeds the normal range (around ten minutes or more), it's best not to ignore it and take the car to a professional repair shop to check the electrical system promptly, to avoid affecting the battery's lifespan or causing major malfunctions.
As someone who frequently tinkers with cars, I think it's a common phenomenon for the fan to keep running after the key is removed. This is mainly because the engine remains hot after parking, and the fan needs to continue running to maintain cooling. Generally, it's designed to run for a short while and then stop automatically. However, if the fan doesn't stop, the issue often lies in the control mechanism: the temperature sensor might be faulty, misjudging the temperature and causing the fan to start erroneously; or the relay contacts might be burnt and stuck, preventing them from disconnecting and keeping the fan running. If this problem persists for a long time, it can easily drain the battery or even damage the motor. When I encounter this issue, I usually use a multimeter to check if the voltage in the fan-related circuit is normal and listen for any abnormal sounds from the relay. But for regular people, I recommend going to a 4S shop for a safety inspection, as DIY repairs can be too complex and potentially risky.
