Why does my Cooling Fan Keep Running after Car is Shut OFF?

Cooling fan running after car is shut off

Why does my Cooling Fan Keep Running After the Car is Shut Off?

The cooling fan in your car keeps running long after the car is shut off due to a overheating or fault with the relay. 

The reason behind this could be faulty temperature sensors or some issue with the cooling fan or ECU unit.

  • Faulty Temperature sensors
  • Faulty within the ECU unit


The cooling fan usually shuts off within a few minutes of the engine being shut off.


Temperature Sensors

A faulty temperature sensor can also cause this problem. The coolant fans run based on the feedback obtained from the temperature sensors. If the sensors are faulty, then it could be giving out wrong readings, thereby forcing the fan to keep running.


ECU unit

The general principle is that the ECU unit tells the fan to keep running if the coolant system is still hot. The ECU unit connects to the ground and tells the fan when to switch ON or switch OFF. If the ECU unit has some fault, then it cannot tell the cooling fan when to switch OFF. 

The fan runs to dissipate the heat. So it is not normal for the fan to keep running after the car is shut OFF. This needs to be checked out by a car mechanic.


Why Does My Radiator Fan Not Turn Off?

The radiator fan might not turn off due to a faulty radiator control module, issues with the cooling fan, or the temperature sensor. You can easily identify what is causing this issue by following a few simple steps.

  • Remove the temperature sensor. This is usually found under the distributor. If you find that the fan stops running immediately, the issue lies with the sensor.
  • Check for a faulty radiator control module and do a replacement. This module is normally located near the glove box.

Look out for a stuck cooling fan relay. Usually, the cooling fan relays work with direct power. A closed or stuck relay can cause the fan to keep running. Replacing the relay will usually solve the issue.


How Long Should A Car Fan Run After The Car Is Turned Off?

The consensus is 5 minutes as to how long the car fan can run after the car is turned OFF. This usually varies from model to model and for how long the car has been driven.

If the car has been driven for a long time, it might take a little more time for the cooling fan to shut OFF. 

The fan dissipates heat and lets the engine cool down. Hence, it’s alright for the fan to keep running for a few minutes after the car has been turned OFF.

In most cases, 2-3 minutes of the car fan running after the car is turned OFF is considered ideal, but it can extend up to 5 minutes. Anything above this limit indicates some sort of an issue with the car. If your fan continues to run longer than 30 minutes, disconnect the battery terminal, (especially the negative side). This will prevent the fan from draining out your battery. 


Should The Radiator Fan Be Running All Time?

No, the radiator fan shouldn’t be running all the time. It should run only when the engine is started and not after the engine is shut OFF.

The main purpose of a radiator fan is to help maintain the ideal temperature of the engine. 

The car engine should maintain the correct temperature for it to work efficiently. A radiator fan helps in achieving this. Under normal circumstances, the fan doesn’t start running as soon as the engine is started as there is no heat to dissipate. It starts running a few minutes after the engine is started.

If you find that the temperature gauge on your dashboard is indicating a high temperature, then you might find that the fan keeps running even after the engine is shut OFF. It might be a good idea to take a look at the coolant level. Usually, when the coolant is very low, the temperature shoots up. This could be due to a coolant leak or a clogged system.


How Often Should The Cooling Fan Come On?

The engine cooling fan should come ON when the engine has been idling for more than 20 minutes. 

The cooling fan is connected to a temperature switch which controls how often it should be started. Usually, there is a temperature cutoff above which the cooling fan will automatically turn ON. 

Ideally, you can do a simple check to see when the cooling fan turns ON.

  •  Switch OFF the AC and start the car.
  • Wait till the temperature gauge reading reaches the normal operating temperature. At this juncture, the cooling fan usually turns ON. The coolant heats up and reaches a temperature above 200 degrees.
  • If the temperature gauge reading is above the optimum temperature or the temperature rises too fast, you need to get the coolant levels checked. Low coolant levels can cause the engine to get heated very fast. This can lead to issues with the engine.


Should The Radiator Fan Turn On When AC Is On?

Yes, the radiator fan that is connected to the AC system should turn ON as soon as the AC is ON. The AC works to keep the car cool.

This means that the fan helps in bringing about the cooling effect. On the other hand, the fan that is connected to the coolant and the temperature system will turn ON only when the temperature rises above a certain level.

An AC works on the principle of heat exchange. The heat from inside the car must be released to let cold air into the car. The AC compressor pushes the refrigerant, which in turn turns the fan ON. The rotating action of the fan helps in the heat exchange process, thereby cooling the interior of the car.

In simple terms, if the fan doesn’t turn ON when the AC is turned ON, the car will remain warm. So, the fan must keep running in order for the car to become cool.


How Do I Know If My Cooling Fan Relay Is Bad?

The first sign of a bad cooling fan relay fan is an abnormal temperature rise in the temperature gauge. If the temperature shoots up too fast and goes above the normal limit, then it could indicate an issue with the cooling fan relay. 

Another sign of a bad fan relay is the fan not functioning at all or the fan functioning improperly. If the cooling fan doesn’t get switched ON even after 15-20 minutes of starting the car, then it could indicate a potential issue with the cooling fan relay. 

If the cooling fan doesn’t get switched OFF even after the car has been shut OFF, then again there could be a problem with the cooling fan relay.

These are signs that must be checked with a car mechanic on priority as the engine getting overheated can lead to permanent trouble with the engine.


What Does A Bad Radiator Fan Sound Like?

A bad radiator fan will give out weird noises. Radiator fans are designed to work smoothly unless they are bent or have some other issue. If your radiator fan gives out whirring sounds, you might need to check if any of the blades are out of shape.

Bent radiator fan blades make different noises while running. If you notice the sound from the fan changing suddenly or the fan making some sort of clicking noise, it could mean that the blades are bent. You can try to straighten the blades yourself or get someone to do it for you. If the blades cannot be straightened out, then you may need to replace the fan with a new one.

You can open the hood of your check and see if the fan blades are bent. Even a mild bend in one place can cause the fan to vibrate while switched ON. 


Can You Drive With A Bad Radiator Fan?

Yes, you can drive for short distances with a bad radiator fan, but it’s not recommended.  Driving a car with a bad radiator fan can overheat the car engine.

The radiator fan keeps the engine operating at the right temperature, thereby preventing any overheating issues. Running the car without a functional radiator fan paves the way for disaster as the car could easily overheat.

Most of the fans are controlled by the thermostat. This means that if the fans didn’t run, then the problem lies either with the thermostat sensor or with the fan itself. In either case, it is really bad for the car. If the car heats up too much, the radiator can start spilling out the coolant. In the worst case, the engine can get repaired. This can cost you a lot of money for the repair itself. The safer side would be to get the fan checked immediately.


Do Both Cooling Fans Run At The Same Time?

Yes, both fans will run at the same time. One fan is controlled by the AC while the other is controlled by how much the engine gets heated. If you have been driving for some time and have the AC ON as well, then both the fans will run.

If you are idling and only the AC is ON, there are chances that only the AC cooling fan will run. The same can happen vice versa as well. If you are driving on a freeway and don’t have the AC switched ON, then there are chances that only the radiator fan will run.

Any issue with the cooling fan relay can cause either one or both the fans to stop working properly. If any one of your fans isn’t working correctly, you will need to check the cooling fan relay to know the cause of the problem.

How To Fix A Cooling Fan That Keeps Running?

If your cooling fan keeps running even after the engine is powered OFF, then it could indicate a problem with the relay system.

You can try these steps to assess what the issue is and to fix it quickly.

You need these tools to fix the cooling fan issues.

  • A stick to measure the coolant levels
  • An ohmmeter to check the resistance
  1. Check the coolant levels in your car. If they are low or there is any leakage, the fans could keep running even after the engine has been powered OFF.
  2. Check the coolant temperature sensor. If the sensor is not working correctly, you have to change it, and the problem will most likely be resolved.
  3. Check for a bad radiator relay and replace the bad relay with a new one to get the fan to stop running after the engine is shut OFF. You can use an ohmmeter to check the resistance of the relay. If it isn’t constant, then the problem lies with the relay.

In general, coolant leaks and faulty temperature sensors are the cause for most of the overheating issues. These can cause the fan to run long after the car has been switched OFF.

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