There are a lot of questions that people have about their cars, and one of the most common is “why does the engine fan stay on when the engine is turned off?” This is a pretty complex question with a variety of answers.
In this article, we will explore some of the possible reasons why your engine fan stays on even when your car isn’t running. We will also provide some tips for how to fix the issue if it’s happening to you. Keep reading to learn more!
The engine fan of your car stays on when the engine is turned off because that is exactly what should happen. It is indeed perfectly normal for the engine fan to stay on for a few minutes after you have turned off your car’s ignition.
If you notice the engine fan still running after a couple more minutes, that is when you should be concerned. That then becomes a problem that needs to be fixed.
The mechanism of the engine fan remaining on for a few minutes even after the car’s ignition has been turned off started in the early to mid-1990s. In many cars, the engine fan stays on for anywhere between two to three minutes after the engine is turned off. In other cars such as the BMW and Mercedes-Benz, the engine fan can stay on for even up to five minutes.
So you see, it is okay for the engine fan to run for some minutes after you have turned off your car’s ignition. As I mentioned earlier, it only becomes a concern when the fan runs for more minutes than expected, for instance, anywhere above 10 minutes.
If the fan stays on for a prolonged period, it will drain your car’s battery. It also means there is an electrical issue with your engine that needs to be attended to immediately.
How does the engine fan of your car work while driving and when your ignition is turned off?
When you are driving and of course, your engine is running, the coolant circulates and flows to the radiator. This will lead to the dissipation of heat and thus the engine fan helps to cool this heat while you drive.
When you turn off your ignition and your engine stops running, the coolant does not circulate anymore and the heat stays trapped inside. This will mean that the engine will take a longer time to cool down, making it even hotter in comparison to when you were driving. In this case, the engine fan will have to keep running to cool down the engine.
Why your engine fan may be running longer than usual
As I previously mentioned, if your engine fan runs for about 10 minutes even after you have turned off your car’s engine, then there is a problem. Below are therefore some of the reasons why this could be happening.
1. Low coolant level
The first reason why your engine fan is running longer than usual might be because of low coolant levels. If the coolant level is low, it will take longer for the engine to cool down and thus the engine fan will have to run for a longer time to try and cool the engine.
A coolant level is considered low when it is below the minimum line. You can easily check this by opening the coolant reservoir and taking a look. If it is low, you will need to add more coolant. In case you don’t know where to locate the coolant you can check your car’s manual or ask a professional.
2. Leaking coolant
Another reason why your engine fan might be running for an extended period is due to leaking coolant. If there is a hole or crack in the radiator, it will cause the coolant to leak out. This then means that there will not be enough coolant to cool the engine and thus the engine fan will have to run for a longer time.
A leaking coolant might be caused by a variety of factors but is not limited to, a hole in the radiator, a loose hose, or a faulty thermostat. In case you notice any leaking coolant, it is important that you take your car to a professional as soon as possible to have it fixed.
3. Faulty cooling fan relay
Another reason is a faulty cooling fan. The cooling fan relay is responsible for sending power to the engine fan. If this relay is faulty, it will cause the engine fan to run for a longer time than necessary in an attempt to cool the engine.
Corrosion, overheating, or just general wear and tear are mostly the main causes of a faulty fan. If you suspect that the cooling fan relay is the reason why your engine fan is running for too long, you should take your car to a professional who will be able to test it and replace it if necessary.
4. Faulty cooling fan
As the name suggests, the cooling fan helps to cool the engine by blowing air over it. If this fan is not working properly, it will not be able to cool the engine effectively and thus the engine fan will have to run for a longer time.
A faulty cooling fan can be caused by several factors such as a broken blade, an electrical problem, or a blockage in the airflow.
5. Defective powertrain control module (PCM) or electronic control unit (ECU)
Again, another reason might be due to a defective PCM or ECU. The powertrain control module is responsible for controlling the engine, transmission, and other aspects of the car. The electronic control unit, on the other hand, is in charge of operating different electrical components in your car such as the lighting system, windows, and doors.
If either of these modules is not working properly, it can cause the engine fan to run for a longer time than necessary. Both the PCM and ECU can be damaged by water or corrosion.
6. Cracked radiator
Another factor might be because of a cracked radiator, which will not be able to hold the coolant properly and thus cause it to leak. A radiator is an important component of the cooling system and needs to be in good working condition for the car to run properly. A cracked radiator can be caused by several things such as overloading, poor maintenance, or an accident.
7. Leaking thermostatic housing
Again, the thermostatic housing can cause the fan to run for long because the thermostatic housing is responsible for regulating the flow of coolant to the engine. If this housing is leaking, it will cause the coolant level to drop, and thus the engine fan will have to run for a longer time.
8. Leaking heater core
The heater core is responsible for heating the cabin of the car. If this core is leaking, it can cause the coolant level to drop, and thus the engine fan will have to run for a longer time. A leaking heater core can be caused by several factors such as corrosion, poor maintenance, or an accident.
9. Faulty electrical wires
Faulty electrical wires are also another possible reason. If the wires that connect the engine fan to the battery are damaged, it will cause the engine fan to run for a longer time than necessary.
10. Engine overheating
The last reason I will mention is engine overheating. If your engine is overheating, it will take longer to cool down, and thus the engine fan will have to run for a longer time.
Engine overheating can be caused by several factors such as low coolant levels, leaks, faulty components, or blockages. If you think that your engine is overheating, you should take your car to a professional who will be able to diagnose and fix the problem
These are some of the possible reasons why your engine fan might be running for a longer time than usual.
What to do if your engine fan is not running off after a while
1. Disconnect batteries
The simplest thing to do if your engine fan will not go off after having turned off your engine for say 10 minutes, is to disconnect the car’s battery cable’s negative side. This will help save the battery or else it will get drained i.e. your battery will die.
2. Add coolant
Moreover, if you realize it is your coolant level that is low, you can add some more. A low coolant level leads to a hotter engine and thus will need the fan to work more often to keep the engine cool. This is why your fan may stay on for a longer period even after you have turned off the ignition.
3. Check engine fan relay
Furthermore, you can also use a digital multimeter to check the operation of the engine fan relay. In this case, if the fan turns off, then the relay is faulty.
4. Test fan relay
Another thing you can do if your engine fan will not go off is to test the fan relay. If that is the problem, a mechanic or engine specialist can swap the bad fan relay with a good one with the same pin design.
To conclude this article, when the engine fan is still running a few minutes after you have turned off your car’s ignition, it may not necessarily be an issue. This is because the fan will be working like it was designed to.
There is a thermostatic switch that turns on and off the engine fan at a certain temperature. Once that switch is working perfectly, there is no cause for alarm.
When you stop your car i.e. turn off the ignition, the fan has to continue working to cool the water in the radiator and it will only go off when the temperature goes down to the appropriate temperature.
I hope this article was able to help you understand the working of your car’s engine fan and why it may stay on even after you have turned off the ignition. If you have any further questions, please feel free to reach out to us. I would be happy to help!