Fan Still Running When Car Is Off – Causes and Fix

If the radiator fan is still running when you shut off your car’s engine, don’t worry. This usually happens to many vehicles. To help you understand, I’ll discuss why fans are still running when the car is off – causes and fix. 

One of the reasons why the fan still runs even after you shut the engine off is an extra hot engine. Maybe your coolant level is low, which can lead to reduced cooling in the cooling system. This forces the fan to do extra work to cool the engine. As such, the fan keeps running even after you shut the engine off.

Before this happens, you will notice some signs. One of the common symptoms is the engine overheats. Some other symbols include a shorted signal wire and the Check Engine light on your dashboard suddenly coming on. 

Read on to learn more about why your car fan is still running even after turning the engine off, the possible reasons, and how you can fix this problem.

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Fan Still Running When Car Is Off

fan still running when car is off

Might Be Due to an Overheating Engine

Don’t be overly worried when the radiator fan of your car may still keep on running even after you have turned off the engine. This is a regular occurrence in car engines. There are several reasons why this can happen, and there are also appropriate fixes for this problem. 

One of the reasons why this can happen is if your engine is overheating. Your engine is probably overheating because the coolant level on your cooling system is already low.

Radiator Fan Will Work Overtime

This leads to the fan working overtime to keep the engine cool. That’s one reason the fan still runs when you turn off the engine.

Car engines are designed to run optimally when hot, but not overly hot. The fan provides a cooling effect so the engine won’t overheat. When you turn off the engine, the fan is supposed to stop, and cooling air will no longer flow into the engine bay.

This will cause an increase in the engine temperature, which usually causes to fan to run still. It usually happens with vehicles such as:

  • BMWs,
  • Toyotas, and
  • Mercedes-Benzes.

The fan may run extra time for about three to five minutes.

Not Flowing Coolant

Typically, the coolant circulates throughout the cooling system. When the engine runs, it flows to the radiator, which expels the heat. However, there are times when you turn off the engine, and the coolant does not flow.

This situation keeps the heat trapped in the system, which delays the ability of the engine to cool down. So, even if the engine is turned off, the fan keeps running for a few minutes to help cool the engine.

However, if the HVAC fan of your car persists in running even if your engine is not overheating, you can manually override its automatic system. Just turn off the fan limit switch by setting it to manual override, and the fan will stop running.

Why Won’t the Fan Turn Off?

If you allow the fan to run long after the engine is turned off, your battery will be drained of its juices. So, you need to take care of this issue. First, you need to know the probable cause of why this can happen. There are several reasons for this:

1. Low Coolant Level

If the coolant level is too low, you can experience this problem. Your battery will be drained out entirely because it is the only one that sustains the operation of the fan when you have already turned off the engine.

The coolant level may go down dangerously if there’s a leak in the system or the coolant reservoir. So, those are the first things you need to check if your fan is working extra time.

Check the coolant reservoir if it is already below the minimum mark. Checking the cooling system will be a lot more complicated. A professional HVAC cooling technician should do it.

2. Electrical Wiring Issues

There are also instances, though rare, where problems in the electrical wiring of the cooling system are the culprit. Perhaps the wires are wrongly connected or damaged. They will lead to the malfunctioning of the cooling system.

In such cases, the only way to solve the fan problem is to check where the wires are misconnected and correct the connection immediately. Hopefully, the fan will stop running when you turn off the engine. If it still runs, then there must be another problem.

3. Leaks

Leaks in the coolant or its system can be in many forms. It can be a malfunctioning thermostat, a loosely connected hose, or a hole or a crack in the radiator. Any of these things can cause the coolant to leak out of the system, which yields its level to go down.

As a result, the fan will continue running as it tries to keep the engine temperature at the optimal level.

Click here to see this coolant leak repair on Amazon.

4. Bad Temperature Sensors

The coolant system uses several sensors to manage the operation of the cooling system components. They are installed near the engine thermostat. Their work is to measure the coolant or thermostat release temperature.

The sensors relay information or signals about the engine’s operating temperature to the control system. Your car’s computer system will then use the information or data about the engine’s operating temperature to modify or continue how the engine works.

This is so that the cooling system can run continuously at the correct operating temperature. At this point, the cooling fan may turn on or off when the control system receives the data it receives from the sensors.

For instance, it can send signals to open the recirculation of the gas. This then leads to the fan working continuously for an extended period after the engine is turned off. Checking the condition of the sensors will help fix this issue.

5. Bad PCM or ECU

If your car’s power control module (PCM) or electronic control unit (ECU) is malfunctioning, it could also cause the cooling fan to keep running after you turn off the engine.

The ECU is responsible for the efficient operation of your car’s many electrical components, while the PCM takes control of the engine, transmission, and other parts of your vehicle.

If PCM or the ECU or both of them are faulty, it can cause the fan of your cooling system to operate even after you have shut off the engine. Many things can cause these two electrical systems to go wrong.

There will also be instances when these two electrical systems are not able to recognize or interpret correctly the signal or information they receive from the temperature sensor. In such cases, they can mishandle the operation of the cooling fan. 

6. Damaged Radiator

If the radiator is damaged, it cannot operate efficiently. Damage can be in the form of cracks in its parts or structure or deformities or leaks in its fins.

Any one of these defects can cause it not to work correctly. The result: the radiator or cooling fan may still run after you’ve turned off the engine.

Click here to see this radiator leak repair on Amazon.

7. Bad Fan Relay

Another potential cause of the problem is a malfunctioning fan relay. It is the switch for the cooling fan of the engine. If this relay experiences any problem, it won’t be able to transmit the information it receives from the temperature sensors or the ECM.

8. Leak in the Heater Core

The heater core is in charge of heating the car cabin. If there’s a leak in the heater core, the coolant level will drop, and the fan will keep running for some time. A leak in the core can occur due to damage, poor maintenance, or corrosion.

Again, why does your fan stay on when you turn your car off? A fan still running when the car is off might be due to a low coolant level or a leaking water pump.

What Can You Do to Fix Fan Still Running When Car Is Off Issue?

fan keeps running when car is off

This problem can be fixed. Here are several things that you can do to solve this problem:

1. Top Up the Coolant

Check the level of the coolant in its reservoir. If it is below the minimum level, top it up. Be sure you use the same coolant type inside the reservoir. Monitor the coolant level to see if the correct level is maintained for a reasonable length of time.

As you keep driving your car, the coolant level will naturally decrease. However, if it goes below the minimum level in just a short time, there is probably a leak in the system. That is the reason why your coolant level is going down so fast.

This will cause your engine to overheat, aside from our current issue of the cooling not turning off after you have turned the engine off.

2. Disconnect the Battery

By disconnecting the car battery, the cooling fan will quickly shut down. Do this by disconnecting the negative cable from its battery terminal. This will prevent the draining out of the battery’s juices.

3. Check the Fan Relay

To check/test whether the relay you are using is working or not, swap it with a relay you know is working.

If the new relay stops the fan from running when you turn off the engine, then the relay that you are currently using is no longer working. You need to replace it with a new relay of the same specs.

Another way is to use a multimeter to test the fan relay’s condition. Test for continuity in the existing relay. Use the resistance mode of the multimeter. Put the ohm range in the minimum range. Connect the leads of the multimeter across the relay coil terminals.

The multimeter will read from 40 to 120 ohms if the relay works fine. If the relay is bad, there is no continuity, meaning it is open and cannot carry any electrical input. You have to replace it.

How Much Will It Cost to Fix a Defective Cooling Fan?

why does fan run after car is off

If you need to replace a defective engine cooling fan, it may cost between $300 and $400. The actual cost depends on the brand and model of your car. The repair or replacement work is very straightforward.

If you are handy with ordinary repair tools or gadgets, you can even do it yourself and save on labor costs, which eat a large part of the total repair/replacement cost. Refrain from using a defective cooling fan because it may cause harm to your engine, which can cost you more to repair.

In Closing

Your car’s radiator fan may keep running after you turn off the engine, probably because of the overly hot engine temperature. This extra heat forces the fan to do more work to cool down the engine, even if it is already off. 

There are some signs before this thing happens that you should watch out for. One of the symptoms is if the engine overheats. Other symptoms that may manifest are the Check Engine light on your dash turning on or a signal wire being shorted.