The Radiator Fan Running When Truck Is Off, What To Do?

The cooling fan in your car keeps running even after the car is shut off. Because of the overheating or fault with the relay. Learn more about why your radiator fan running when truck is off.

Reason Behind Radiator Fan Running When Truck Is Off?

The reason behind the fan running when the truck is off could be faulty temperature sensors or some issue with the cooling fan or ECU unit. The radiator fan might not turn off due to a faulty radiator control module, issues with the cooling fan, or the temperature sensor.

1. Faulty Temperature Sensors:-

A faulty temperature sensor can also be the reason behind this problem of radiator fan running when truck is off. The coolant fans run based on the feedback obtained from the temperature sensors. If the sensors are faulty, then they could be giving out wrong readings, thereby forcing the fan to keep running.

2. Faulty Within The ECU Unit:-

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.

3. Faulty Radiator Control Module:-

The module helps to make sure that the cool air that is produced within the A/C system of a car is blown into the cabin. The A/C fans that are mounted near the radiator of the car are also controlled by this module. Usually, you will have a variety of signs that the A/C fan control module is going out. If the cooling fans begin to run erratically, then you may have a problem with the control module.

How Long Should A Radiator Fan Run After The Car Is Turned 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. This will prevent the fan from draining out your battery. 

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.

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. 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 running when the truck is off.

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. 

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.

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?

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.

How To Fix This Issue Of Fan Keeps Running When Engine Is Powered Off?

If your cooling or radiator 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.

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 of most overheating issues. These can cause the fan to run long after the car has been switched OFF. 


We hope the above-mentioned information about the radiator fan running when truck is off will be helpful to all the viewers. If anybody’s doubts persist feel free to comment in the comment section below. We’ll try to solve your doubts as soon as possible.

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