There are a number of reasons why your car may be overheating and the fan will not turn off. Here are some common reasons for this to happen:
The temperature gauge in your car is broken and stuck at hot. If the temperature gauge in your car is broken and stuck on high, then it can lead to overheating issue that causes the fan to stay on after shutting off the engine. You should get this checked out by a mechanic or someone who knows how to fix cars.
Loose coolant hose
A coolant hose has come loose or burst. A coolant hose holds coolant (water) which goes through the radiator and absorbs heat from the rest of your engine; when it does this it becomes hot. When the hose is loose or burst, coolant will often leak out and this can cause your engine to overheat, which will again lead to the fan staying on after you turn your car off. The only solution here would be to get a new hose fitted
Broken cooling Fans
Your engine’s cooling fans are broken. There are three different types of fans within an engine that keep the temperature down by drawing air into the system through the radiator. If one of these fans fails then what happens is that there isn’t enough air passing through to cool everything down, so the temperature inside begins to go up quickly. Again this leads to overheating issues which can cause your car’s fan to stay on even when you have turned off your vehicle. You will need to get a fan replaced for this.
Your engine is overheating. It can be that your engine is simply overheating and causing the cooling fan to stay on after you have exited the car. If this occurs, then a number of things could be wrong: there may be a massive hole in your radiator (so coolant is leaking out) or maybe there’s not enough water in your radiator, or even that your thermostat has failed. All these problems would require an expert mechanic to fix them.
If none of the above reasons apply, remember when you are asking yourself This only happens when my car’s fan still running after I turn my car off then the only thing you can do is to check if this problem occurs in both cold and hot weather. If it does, then try asking yourself:
Are there any warning signals in my dashboard when this happens?
What about during your journey? Does your fan still running when the engine is not heating up or when you step on the accelerator pedal? If no, then most likely no issue with your fan. It might be caused by how you drive (when you accelerate).