Is it normal for a car fan to still be on after the engine is turned off? Yes, your car’s engine cooling fan could still run for a few minutes after you’ve turned off your car’s engine. It’s understandable to ask this question because it’s safe to assume that when you turn an engine off, it does just that.
But sometimes, the cooling fan can keep running for a few more minutes after you’ve shut down the vehicle. Why does this happen? Why doesn’t the fan cut off the moment you cut the engine? First, we have to get some idea of how your car engine’s cooling fan system works.
The purpose of a car’s engine cooling fan is to move air through the radiator when the car slows or stops. As the air flows through the radiator, it eliminates the heat produced by the car’s engine. So, when you turn off your car’s engine but the sound of the fan still at work is audible to you, that’s because it’s getting rid of “leftover” heat since the coolant stops circulating when the engine is turned off.
Just like the fan can still be running after you’ve turned off the engine, the fan does not kick in immediately after you turn on the engine either. That’s because the cooling fan in your car is temperature-controlled. What this means is that the cooling fan will only run when necessary.
It’s safe to point out that the radiator will overheat if it isn’t getting constant air. So, while it’s possible to drive your car without a cooling fan present, that’s not a good idea.
Even so, a car’s engine needs to warm up for optimum performance. Therefore, the cooling fan is designed not to turn on as soon as the engine turns over. Instead, a cooling fan that is operating at its peak will turn on when the engine’s heat level exceeds the normal operating temperature and turn off when the opposite is the case.
To generalize, the fan should turn on when the radiator produces heat of about 200℉. However, every engine has its preferred operating temperature. So, the reason you could still hear your car’s cooling fan after you’ve turned off the engine is because it’s “working late” to get rid of the heat trapped in the condenser while you were enjoying the air conditioner.
It’s safe to say that not all vehicles behave this way, though. But if your car’s engine—especially Mercedes-Benz and BMW—goes to sleep before the cooling fan does, it’s perfectly normal. It’s okay for the fan to keep going for up to five minutes or longer. But you may have a problem if the cooling fan stays on for longer than ten minutes after you’ve cut the engine, especially because overuse can cause damage to the fan itself.
There is a long list of what might be wrong if the fan is staying on longer than is normal. It could mean a low coolant level, bad radiator fan relay, leaky thermostat housing, defective PCM or ECU, or defective coolant temperature sensor, among others. Finally, if the fan won’t turn off until the battery is drained, then the car must have an electrical problem. So if your fan won’t turn off for 10 minutes or longer after you’ve cut the engine and your coolant is full, you should consult a mechanic.