Radiator Fans

5 Causes of Radiator Fan Is Not Coming On

In Electric by 15 Comments

You probably already know the purpose of the radiator and the cooling system in your car.

When you are driving fast, the wind is passing through the radiator to cool the coolant down without issues, but when you are driving slow, there is no wind pushed through the radiator. This is why we use a radiator fan.

Unfortunately, the radiator fan can fail and will cause your car to overheat. But what can cause this?

The most common causes when a radiator fan is not coming on is broken fuse, bad wirings, bad coolant temperature sensor, bad fan relay, or a faulty radiator fan.

Here is a more detailed list of the most common causes of a radiator fan not coming on.

1. Broken Fuse

Broken Fuse

A fuse supports almost everything electrical in a car. If there is an electrical surge going towards a piece of electronic equipment, the fuse cuts the electric supply to that particular equipment saving it from destruction. This is what we call a blown fuse.

A blown fuse is no big deal, and changing one does not cost a lot of money. If your car’s radiator fan is non-functional, check your car’s user manual and locate the fuse for the radiator fan controller or the fan.

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The fan itself often uses a big fuse of around 50A, while there might also be a separate small fuse to the fan control module. Remember that if the fan fuse is blown – there might be a problem with the wirings or the radiator fan.

2. Faulty Coolant Temperature Sensor

Coolant Temp Sensors

There are often two different systems in different car models. Either your fan control is integrated into the engine control unit or you have a separate fan control module. In both cases, the control units use a temperature sensor to know when to start the radiator fan.

If this temperature sensor is broken, the control unit will not know when to start the radiator fan.

Some cars use separate engine coolant temperature sensors for the radiator fan and the engine control unit.

You need to check your repair manual of which temperature sensor controls the radiator fan and then resistance-measure the sensor with a multimeter to make sure it is functional.

3. Broken Wiring or Bad connection

Broken Wire

If the fan is not working even when the car is overheating, there might be a wiring issue or a bad connection.

Check the wirings going to the radiator fan from the control unit or relay. Check in the connector plugs for any signs of corrosion. Also, check the connector plugs at the relay and control unit.

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Measuring the wirings with a multimeter is often not very effective, as you need to put a load on the wires to see if they are functional. However, as a fast test, you can check with a multimeter if there is coming power to the radiator fan.

4. Insufficient Coolant

Low Engine Coolant

If your coolant level is low, there is a chance that you will get air in the system, and the coolant temperature sensor will not read the coolant temperature correctly. If the coolant level is low, you need to refill the coolant to optimum levels.

Failing to do so could risk your engine becoming overheated and seized. There is no coming back from a seized engine unless you are willing to spend a lot of money.

5. Broken Radiator Fan

Radiator Fan

When your radiator fans are not coming on, it can also be caused by faulty radiator fans. The radiator fans have electrical motors inside of them, which will wear out after some years.

You can test the electrical radiator fans by taking a wire from the car battery, unplug the radiator fan connector, and put 12v+ and ground into the connector. This is the fastest and easiest way to test your radiator fans.

6. Faulty Fan Relay

Bad Relay

Because the radiator fan is often drawing so much power, there is often a relay that is powering the coolant fan. Of course, this relay can get damaged, which will cause the radiator fan to not coming on.

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The fan relay is often located in the engine bay’s fuse box, but the best way is to check your repair manual to find where it is located.

Testing a 4 pin relay is often very straightforward. Remove the relay and give 12 volts to pin 30 and 85. Ground pin 86 and check if there is voltage coming out from pin 87. It is even better to connect pin 87 to something that draws a lot of power, like the fan, for example.

7. Bad Fan Controller Module

Fan Control Module

As I talked about before, some cars have a separate control module for just the radiator fan control. This control module is often installed in the engine bay, exposed to heat and dust. This can make the control module to fail after a while because of corrosion.

Locate the relay and check for any visual damages outside of it. You can often also open up the relay and check for any bad solderings or corrosion. Replace it if you see any problems.

15 thoughts on “ 5 Causes of Radiator Fan Is Not Coming On ”

  1. My problem is that the fans work when I start the vehicle but when it warms up, they no longer work! It is getting dangerous to blowing. Right now I am parked waiting for rush hour(s) to finish. Very annoying. Already replaced the fans, radiator, temp sensor and relays… I’m fitting to cut the wires and run them directly to the battery w a switch before I loose this vehicle!

  2. run a 12volt wire with a switch and just turn your fan on when it is starting to get to warm or when it needs to be on

    1. I have Toyota camry 2014 always factory maintained. After parking the car for 15 20 minutes with ac on its engine temperature goes to half and ac trips and radiator fans are off.
      When switch off the car and restart all gets fine again.
      Please advice.

  3. Thanks for your writing it’s encouraging am happy .In my car my car is suzuki Every bus the radiator fan fuse cuts often when ever i pass through water because our road water loged please help thanks

  4. hello

    I have Subaru forester 2004. The issue is with the coolant fan. it wont turn on eventhough I have replaced the temp sensor with a new one. I have checked electricity with test meter and the wiring is okay. The fan does work when you turn on the AC

    Can anyone help with this problem.

  5. Hey there i just bought used peugeot 508 and have one issue with it. The fan doesn’t work when the engine is off, it only run when i turn on the engine. Could you please help me with this.


    1. My Nissan np200 heater does not blowing warm or hot air i ‘ve even changed the old thermostat and replace with new one but still the same please help.

      1. It sounds like either low antifreeze, or possibly a bad vaccume line, that usually opens a valve, so hot antifreeze is allowed to flow flow thru heater core, in some older cars, or possibly a cable, not sure here, but thought I would throw it out there.

  6. Hi, it’s Ayanda
    I m driving proton gen 2.
    Radiator Fan is not working and the car’s temperature goes to 130, I don t know what to do

    1. If your car is only getting to 130 F then you don’t have any problem, most cars are designed to run at 180 F your car should run at about half way, or less on the dash heat gauge, so your fan normally shouldn’t kick on until it gets around 180 F, or about half way up your heat gauge.

  7. I have a 2007 Nissan Altima, several months ago the ac compressor clutch went out. Didnt have the money to get a new so I replaced it with a pulley. My car started to over heat, I think the coolant fans aren’t work, my question is Does the ac compressor clutch control the radiator cooling fan?

    1. You can have the other pulleys going in the wrong direction which will cause it to overheat. It’s better to have purchased a shorter belt for the same car without air conditioner.

  8. I have VW Sharan VR6 2,8 engine I can run the engine until is hot 50% or very hot and my engine will cut off and I must wait until it’s cool and I can start and run again what is the problem?

  9. I have a 2005 Buick LeSabre I have dual fans the one on the driver side works and the one on the passenger side does not work. Trying to locate the problem. Does not overheat
    but notice it did not come on

  10. I have a 2008 Nissan march when I start my car and after driving about 5 minutes the red thermometer light comes on the dashboard for about 11 seconds and then goes of what does that mean. Is the car overheating? IT has in enough coolant and the fans are working.

  11. If you need answers to your car questions, it is much more likely that you will get answers in our car community. You can find our community here.

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