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What You Need to Know About Your Car Radiator Fan

What You Need to Know About Your Car Radiator Fan

A radiator fan blows air through the radiator to cool down the engine’s coolant temperature. It’s essential for a car that idles in traffic or travels long distances.

The cooling fans can be either electric or mechanical. Mechanical ones use a clutch and pulley system.

To check your radiator fan wiring when it’s not working, unplug both wires and test for current with a multimeter.

1. Motor

The radiator fan motor is the part that drives the car cooling fan. It’s the most likely part to break down, and for this reason, it’s usually replaced first. Depending on your vehicle, you might have an electric or mechanical fan motor. The cooling fan is a vital component of your engine’s temperature management system.

The cooling fan blows air across the radiator and removes heat from the coolant, keeping it at a stable temperature. Without a working cooling fan, the engine overheats quickly, especially at low speeds or while idling. Overheating damages engine parts and causes expensive repairs.

Your vehicle’s cooling fans are designed to ensure that as much air as possible is drawn through the radiator. This helps the engine stay at a safe operating temperature, regardless of how hot or cold it is outside. The cooling fan is also important for keeping the engine running smoothly and efficiently.

A malfunctioning fan can cause your engine to overheat, car radiator fan so it’s essential that you fix the problem as soon as you notice any signs of a bad fan. To help you, we’ve put together a guide to changing the cooling fan motor on most cars. It’s not difficult to do and you can usually find replacements at your local Natrad store. Whether you have an electric or mechanical fan, this guide will give you the information you need to change the motor.

2. Clutch

Like most automotive parts, the cooling fan clutch will eventually wear out. While there is no hard-and-fast mileage at which this part will fail, it’s important to recognize the telltale signs of a worn clutch, so you can have the issue rectified by your mechanic before it leads to failed engine cooling and reduced power output.

A bi-metallic clutch is used to engage and disengage the engine cooling fan, which operates based on underhood temperatures. When hot air blows across the radiator, it heats up, which in turn causes a thermal spring in the front of the fan clutch to expand and open valve ports inside the clutch. This allows the heavy silicone fluid stored in the clutch to flow through the openings, locking the fan onto the pulley. As the temperature cools, the bi-metallic fan clutch closes and disengages the fan.

A mechanical fan clutch can be found in older vehicles, and it is usually mounted on the water pump car radiator fan pulley on a RWD car or the crankshaft pulley of a front-wheel drive vehicle. When the fan clutch fails, it may freewheel, leading to overheating and a loss of performance, or it can lockup causing noise and vibration. Nissens offers a wide range of quality aftermarket fan clutches that are designed and tested to ensure long-life operation and high levels of modulation for improved fuel efficiency, lower noise and less strain on the engine.

3. Coolant

When your car engine burns fuel, it produces heat that needs to be carried away. The coolant in your car takes the heat and transfers it to air that flows through the radiator, where the cooling fan is located. If the cooling fan motor or fan stops working, your engine can overheat. That can cause significant damage that requires expensive repairs.

Your radiator fan won’t run unless it gets a signal that the engine temperature has reached a specific level. The fan is usually activated by the engine control unit, which receives a signal from the coolant temperature sensor. If the coolant temperature sensor doesn’t function properly, the fan won’t turn on, and your car’s engine can overheat.

The radiator fan draws very little power, but it does have a fuse that can blow if there’s an electrical surge. If the fan fuse blows, it needs to be replaced immediately to keep the cooling system safe from further damage.

Your car’s cooling fans can also fail due to faulty wiring or the fan itself. If you’re not sure which of these issues is at fault, visit a Natrad mechanic near you for professional advice and repairs.

4. Temperature Sensor

Most modern cars have an electric radiator fan that draws power from the vehicle electrical system. These fans are very sensitive to temperature and can be easily triggered to turn on and off as needed. Unlike the mechanical fan clutch on older vehicles, modern fans usually don’t have many parts and therefore are less prone to breaking down. However, there are still problems that can occur from time to time.

A common reason why your car’s cooling fan won’t activate is because of a bad sensor. The sensor is a device that reads the engine’s temperature and sends a signal to the fan to come on based on the coolant temperature. The sensor can be built into the engine control module or it can be a separate part. If the coolant temperature sensor isn’t working, it can lead to overheating and other issues with your car’s engine.

Another reason the fan might not be turning on is because of a blown fuse or a bad relay. These are both easy fixes and can be checked by checking the owner’s manual for the location of these fuses or relays. Also check the wiring connections at these devices for signs of corrosion. Finally, you can try bridging the radiator fan relay with your multimeter and see if that starts the motor.

What You Need to Know About Your Car Radiator Fan

What You Need to Know About Your Car Radiator Fan

A radiator fan is important to keep your engine cool and avoid overheating. There are two types; mechanical and electric. Mechanical fans are clutch-based and attached to the water pump pulley. They can have either straight or flex blades that flatten at higher RPM and engine speed.

A push type fan inhibits the free flow of air to the radiator at idling and low speeds. If you have a dual fan setup a pull type fan is best.


The radiator fan motor takes the heat from the coolant and blows it away to help keep the engine running within its optimum operating temperature range. This is essential for power, efficiency and emissions. When the fan motor fails, air is unable to move through the radiator and the engine overheats. It is possible to drive a short distance if the cooling fan doesn’t work properly, but overheating will cause serious damage to the engine and potentially other parts of the vehicle.

The first thing to do is check that the fuse for the radiator fan has not blown. This car radiator fan could be caused by a faulty fan motor or other problems with the cooling system. If the fuse is OK, then check that the thermoswitch is functioning. You can do this by leaving the ignition switched on and putting a circuit tester across the feed wire to the thermoswitch (do not disconnect the leads). If there is current passing through the switch, it is working.

Next, you can check that the motor is working by putting a test light or circuit tester on its live lead to the relay (with the ignition still on). If there is no current at all, the fan motor is faulty. This is the easiest part of the fan to replace, so it is a good place to start.


The clutch is the part that keeps your car radiator fan engaged and turning at the proper speed to cool the engine. It’s usually made of a tough material like friction-lock or abrasion-resistant polycarbonate. But, just like all other parts of your vehicle, it will eventually wear out. When it does, your cooling fan will stop turning. That’s why it is important to inspect the radiator fan clutch regularly.

You can check for a bad or worn-out fan clutch by looking for several signs and symptoms, including a lack of power when you accelerate or lower engine RPM, overheating, and/or reduced fuel efficiency. You may also notice that your fan is not turning even after the engine has cooled down.

There are two main types of clutches for the radiator fan. The first is the thermal type, commonly found in rear-wheel drive vehicles. The bi-metal thermal spring mounted on the front of the clutch expands or contracts based on underhood temperatures. When the temperature is high, the fan clutch opens a valve that releases silicone fluid into a chamber within the clutch. The liquid then engages the fan to turn it at 70 to 90 percent of the water pump’s speed.

The second type of clutch is the non-thermal type that combines a viscous or fluid coupling with a bi-metal sensor to control engagement. The sensors can be controlled by the ECU and are influenced by inputs such as engine/transmission oil temperature, engine coolant temperature, AC system pressures or ambient air temperature.

Temperature Sensor

Your car’s radiator fan helps cool the engine by moving air over the cooling fins. It’s usually rated in CFM, or cubic feet of air per minute, to indicate how much it moves. For a powerful engine, you’ll need a larger fan that can move enough air to keep the engine from overheating, which can cause expensive damage or even destroy the engine.

A radiator fan is part of the vehicle’s cooling system, along with the radiator, water pump, thermostat, and hoses. When it’s working properly, you’ll hear a whirring noise when the fan is spinning. If the fan stops running, you should check to see if the engine is overheating, which can lead to expensive and potentially dangerous repairs.

The fans in modern cars are controlled by the engine coolant temperature sensor, or a separate fan control module. If the coolant temperature sensor is broken, or if it’s not reading correctly, the fan won’t turn on. A multimeter can be used to test the wiring from the fan to the control module and relay, checking the connector plugs for signs of corrosion. If the wires are good and the fan still doesn’t activate, there could be a problem with the relay or control module. In this case, you’ll need to replace it. You can also try bridging the radiator fan relay to see if it will activate the motor.


Many of the more energy-intensive underhood components of modern vehicles operate with the help of relays. The radiator fan is no exception. Relays are electromagnets that switch on and off by using a small current to close a circuit. This allows the relay to control larger currents without overloading the switch/device it controls.

When the engine running temperature of a vehicle approaches dangerous levels, the computer or car radiator fan temperature switch activates the fan relay. This completes an electrical circuit and lets the relay’s electromagnet anchor attract an electric current that energizes the cooling fans.

The cooling fans (one or two on some cars) pull air through the radiator and coolant system to reduce the engine’s operating temperature. The fans can also pull air through the air conditioner and pass it through the condenser to decrease the pressure of the refrigerant.

When the radiator fan relay fails, the coolant fan motor cannot get the power it needs to run properly. One of the most common symptoms is an engine that overheats while driving or when parked and running at a stop. Another symptom is when the fans themselves do not come on. If the fans are not working, a multimeter can be used to verify that they are receiving power from the relay terminals. If not, a relay from a noncritical system that operates the same way can be swapped out for testing purposes.