Skip the auto shop - Our mechanics make house calls

Symptoms of a Bad or Failing Cooling Fan Resistor

Cooling fan resistor

Virtually all modern vehicles built today use electric cooling fans to help pull air through the radiator to keep the engine cool. Once the coolant temperature sensor detects that the engine temperature has exceeded acceptable levels, the cooling fans will be activated to keep the engine cool. Many vehicles come equipped with cooling fans that operate on more than one speed setting. This is made possible by routing their power through the cooling fan resistor. The cooling fan resistor is an electrical resistor that limits power to the fan in steps, so that the fan can operate at different speeds according to the cooling system’s demands. Since power to the cooling fan is sometimes routed through the cooling fan resistor, when it fails or has any problems, it can cause issues with the regular operation of the fans, which can lead to overheating. Usually a bad cooling fan resistor will produce a few symptoms that can alert the driver of a potential problem that should be serviced.

1. Engine overheats

One of the first symptoms of a potential problem with the cooling fan resistor is engine overheating. If the cooling fan resistor fails or has any issues, it can cause power to be cut off from the cooling fans, which can lead to overheating. Any sort of overheating issue should be tended to as soon as possible to avoid the possible engine damage.

2. Cooling fan speed issues

Another symptom of a possible problem with the cooling fan resistor is issues with the cooling fan speed. If the resistor breaks or has any issues it may cause the fans to only function on certain settings. The cooling fan resistor is meant to send power to the fans in steps, so that the fans may operate at different speeds. If any of the individual steps or switches fail, it will disable the cooling fans from operating on that speed setting. You may notice that the cooling fans only operate at one speed, when they used to operate on two or more.

3. Cooling fans never turn off

Another symptom of a potential problem with the cooling fan resistor is cooling fans that stay on at all times. If the resistor shorts or fails, it can cause the cooling fans to stay on even when they are not supposed to. In certain cases, the cooling fans may even stay on when the vehicle is turned off, and will create a large parasitic drain that will eventually kill the battery.

The cooling fan resistor is an important component, as it is one of the components that routes power for the cooling fans. For this reason, if you suspect that your cooling fan resistor may be having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if your car needs a cooling fan resistor replacement.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

P0222 OBD-II Trouble Code: Throttle/Pedal Position Switch/Sensor B Circuit Low Input
P0222 code definition Throttle/Pedal Position Switch/Sensor B Circuit Low Input What the P0222 code means The manufacturer specifies a range of acceptable voltage to be produced from the throttle position...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...

Related questions

Q: How to change blower resistor

Remove the sound insulation panel located under the right side of the dash, by passenger's footing area. Disconnect connector to blower resistor next to blower motor and remove the two screws. From there you'll be able to remove resistor from...

Q: Car gets hot

This can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning...

Q: Overheating when car is stopped

I am almost certain that the cause of your issue is that your radiator fan is no longer working. I would recommend starting your vehicle and letting it get to operating temperature. After it reaches this point, open your...