Why does the car fan keep running after the engine is turned off?

[DeBrynlee]

The reason why the car fan keeps running after the engine is turned off is: after the car is parked, the engine temperature remains high. When the engine stops, the water pump also stops, causing local temperatures to continue rising. To prevent excessive temperatures from damaging the engine, the fan continues to operate after the engine is turned off to cool it down. Engine classifications: 1. According to the working method of the intake system, they can be divided into naturally aspirated, turbocharged, mechanically supercharged, and twin-charged; 2. According to the piston movement method, they can be divided into reciprocating piston internal combustion engines and rotary piston engines; 3. According to cylinder arrangement, they are classified as inline engines, V-type engines, V-type engines, and horizontally opposed engines.

[Correia]

I've been running a repair shop for almost ten years, and it's very common for the fan to keep running after the engine is turned off. Simply put, the engine temperature hasn't dropped yet, so the ECU automatically keeps the fan running to cool it down. This is especially noticeable in summer after being stuck in traffic, as the radiator accumulates a lot of heat and needs the fan to dissipate the residual heat after shutdown. Some turbocharged cars are even more obvious because they need to protect the high-temperature turbo components. Additionally, hybrid vehicles or cars with frequent auto start-stop rely on the fan for battery cooling systems. As long as the fan stops automatically after a few minutes, there's no issue. But if it keeps running non-stop or spins wildly when starting a cold engine, then you should check the coolant temperature sensor, relay, or electronic thermostat for potential problems.

[OChloe]

This is actually the same principle as a phone still dissipating heat after being turned off. It's quite common for a car's fan to keep running after the engine is shut off, mainly to protect the engine from overheating damage. The engine compartment is like a big insulated box, and after turning off the engine, the heat can't escape. The fan is responsible for blowing away the hot air from the radiator. Especially if you've just driven at high speeds or engaged in aggressive driving, the temperature sensor detects the high-temperature state, and the computer keeps the fan running. My neighbor's German car often does this—he initially thought it was broken but later learned it was a designed protective mechanism. However, if the fan inexplicably runs for more than half an hour, or if you touch the radiator and it's cool but the fan is still running, then it's really time to visit the repair shop to check for wiring issues.

[Silas]

Don't worry, this usually isn't a malfunction but a normal protection mechanism. The engine temperature spikes immediately after shutdown, especially in turbocharged vehicles where it can reach over 100°C. The continued operation of the fan helps rapidly reduce coolant temperature, preventing damage to seals and wiring. Modern vehicles have intelligent temperature control logic—the fan will automatically shut off once the temperature drops sufficiently. However, be concerned if you notice these abnormalities: the fan running unnecessarily during cold starts, coolant boiling, or the dashboard displaying a coolant temperature warning light. Common causes include a clogged radiator, insufficient coolant, or a faulty temperature control switch. Additionally, after using seat heaters in winter, some vehicles' battery cooling systems may also keep the fan running for a short while.