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How to Check if a Radiator Fan Is Working (Step-by-Step)

Updated: Feb 2

✔ This article has been fact checked.

Radiator fans play an essential role in the cooling system of a vehicle. These fans help to dissipate heat from the radiator, which is responsible for cooling the engine. Without a functioning radiator fan, your engine can quickly overheat, leading to serious damage.

To check if a radiator fan is working you should see if the fan turns on if the coolant is hot or if the AC is switched on. If the radiator fan doesn't turn on you can perform a continuity test using a digital multimeter.

In this article, we will outline the steps to check if a radiator fan is working correctly.

Table of Contents:

a car radiator fan up close

What Tells the Radiator Fan to Turn On?

The radiator fan is usually controlled by the engine’s cooling system. As the engine temperature increases, the thermostat will open, allowing coolant to flow through the system and absorb heat from the engine.

If the coolant temperature goes above the target temperature level then the radiator fan is turned on by the fan relay, which is controlled by the engine’s computer.

The fan relay receives a signal from the engine’s temperature sensor, which determines when the radiator fan should turn on.

Types of Radiator Fans

There are two main types of radiator fans: mechanical fans and electronically controlled fans.

  • Mechanical fan: A mechanical fan is driven by a belt that is connected to the engine, it is switched on and off using a type of fan clutch. These types of fans are typically found on older vehicles and are less common in modern vehicles.

  • Electronically-controlled fan: An electronically controlled fan is driven by an electric motor and is controlled by the engine’s computer. These types of fans are more common in modern vehicles and are generally more efficient and quieter than mechanical fans.

radiator fan and shroud

Way to Check if the Radiator Fan Is Working

Use the following methods to see if the radiator fan is working.

1. Check by hearing for the fan to turn on

If the engine coolant is hot and up to temperature, the fan should turn on. You can listen for the fan to start running when the engine is hot. The fan will only turn on if the coolant is above its target temperature (such as on a hot day, stuck in traffic, or after hard driving).

2. Turn on the AC

In some vehicles, the radiator fan turns on by default when the AC is switched on. If the fan does not turn on when you turn on the AC, it may be malfunctioning.

car air conditioning button

How to Check the Radiator Fan Fuse

Follow the step below to check if a radiator is working or not. You will need a digital multimeter (such as these ones) to perform a continuity test.

  1. To test the fuses in your vehicle, you will need to locate the fuse boxes. There may be one under the dash and one under the hood.

  2. Once you have found them, set your multimeter to Direct Current Voltage (DCV). This is because most cars have a 12V battery and are calibrated to take this voltage.

  3. Next, turn off the engine and connect the black lead (negative) to the negative battery terminal. This is for the under-dash fuses. Then, attach the red lead (positive) to a fuse contact. There will be multiple contacts on each fuse.

  4. Look at the reading on the multimeter. If it is around 12V, the fuse is working properly. However, if you get 12V on one contact and 0V on the other, this means the fuse has blown. If you get 0V on both contacts, there is no power connected to the fuse. This could be due to it not being properly connected to the negative battery terminal or ground. In this case, you will need to disconnect and try again.

If you find that a fuse has blown, it will need to be replaced to ensure the fan is functioning correctly.

mechanic holding a car fuse

How Do You Test a Radiator Fan Motor?

To test a radiator fan motor, you will need to perform a continuity test. This will determine whether the motor is functioning properly.

To perform a continuity test, you will need a multimeter set to the continuity setting. With the engine off, disconnect the fan motor’s electrical connector. Touch one lead of the multimeter to one terminal on the connector and the other lead to the other terminal.

If the multimeter beeps, this indicates that the motor has continuity and is functioning properly. If the multimeter does not beep, this indicates that the motor is not functioning properly and will need to be replaced.

When Should a Radiator Fan Turn On?

The radiator fan should turn on when the engine temperature reaches a certain level, as determined by the engine’s temperature sensor.

This typically occurs when the engine is running at high speeds or when the vehicle is stopped and the engine is idling (such as in traffic), it also occurs on hot days and if the engine is pushed and driven hard.

The radiator fan should turn off when the engine temperature decreases to a certain level.


In conclusion, it is essential to ensure that your radiator fan is working correctly to prevent your engine from overheating.

To check if your radiator fan is working, you can check the fuse and perform a continuity test on the fan motor. Make sure to follow the steps outlined in this article to properly test your radiator fan.

There are various symptoms of a bad radiator fan, such as unusual noises, overheating, burning smells, blown fuses, etc.

If you are unable to diagnose the issue or are unsure about any steps, it is always recommended to seek the help of a professional mechanic.


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