Why doesn't the fan run after some cars are turned off?

[DiJosie]

Whether the fan runs after the engine is turned off depends on the coolant temperature at shutdown. It's normal for some vehicles' fans not to operate after turning off, indicating the coolant hasn't reached extremely high temperatures. Here's relevant information: Other situations: Continuous fan operation indicates engine overheating. Common causes for overheating include damaged cooling system components (thermostat, cooling fan), poor radiator performance, or insufficient coolant. Check if low antifreeze level is causing high engine temperature, and verify proper coolant circulation.

[Samuel]

That time I parked my car and turned off the engine, but the fan still wasn't running, which puzzled me. Later, I asked a mechanic and learned that many older cars are like this—the fan is directly connected to the engine, so when the engine stops, the fan stops too, with no smart control. But modern cars are different; the computer monitors the engine temperature, and if the coolant temperature is high, the fan will delay for a few minutes to cool it down. If your car's fan doesn't run after turning off the engine, it's usually because the coolant temperature is normal and doesn't need cooling, or the design is simply to save power. Once the temperature drops, the fan naturally doesn't bother to run, which is quite common in summer after parking.

[SanGriffin]

As a frequent visitor to car repairs, I've observed that it's not unusual for the fan to stop moving after the engine is turned off. The car's fan control is managed by the ECU computer, which determines its operation based on data from the coolant temperature sensor. If the engine cools down quickly or isn't hot, the computer won't send a signal and the fan will turn off. Compared to cars with delayed fan operation, this design saves electricity and protects the battery. However, if the cooling system is clogged or the sensor malfunctions, the fan might act erratically. It's advisable to regularly clean the radiator of dust during normal driving to prevent the fan from failing unexpectedly.

[StJulian]

In terms of design, the car's electric fan is controlled by the ECU for its post-shutdown behavior. After the engine is turned off, the computer immediately checks the coolant temperature. If it's not too high, the fan stops to save battery power and prevent excessive wear. Only when the coolant temperature exceeds the limit will the fan continue running for a few more minutes. This logic ensures the engine remains undamaged. Different brands have varying settings, leading to different performances, but the core purpose is to balance cooling needs with efficiency.