The radiator fan is a critical component of a vehicle that you have likely heard spinning after driving for long on a hot summer day.
However, if the radiator fan has a problem, it could damage your engine if you are not careful. Therefore, fixing the radiator fan is critical as soon as you figure out it does not work.
In this blog post, we cover seven possible causes for the radiator fan not working, how to fix it, and hope this will help you get your vehicle back on the road safely and timely, let’s go!
What Can Cause A Radiator Fans To Stop Working?
The three most common reasons that a radiator fan won’t come on are a blown fuse, bad relay, or broken wire. You may also have a bad coolant temp sensor, low coolant, or a broken fan.
While these are the most common reasons, it’s definitely not an all-inclusive list. Here is an even further expanded list of the most common reasons a radiator fan does not come on:
#1. Blown Fuse.
The fuse controls all the electrical components in your car. If there is an electrical surge going to a certain piece of electronic equipment, the fuse will cut off the electiciy to that piece of equipment, preventing that piece of equipment from destruction. This is what is meant when we say a fuse has blown.
A blown fuse in your car isn’t a big deal, and replacing a blown fuse is cheap. If your radiator fan isn’t working, look in your owners manual for the fuse for the radiator fan controller or the fuse for the fan.
The fan typically uses a large fuse, likely close to 50 amps, and there may also be another smaller fuse for the fan controller module. Just remember, you blow a fuse for the fan, it may be an electrical issue with the cables or even the radiator fan itself. Check further down this article for diagnosis.
#2. Faulty Coolant Temperature Sensor.
Different car models come with two choices of systems. Your fan control is either integrated directly into the motor control unit, or you have a distinct fan control module. The control unit or fan control module will use a temperature sensor that will let it know when to start the radiator fan system.
If this coolant temperature sensor is defective and does not report the engine temperature correctly, the control unit and/or the fan control module will not know to start the radiator fan system. In some vehicle applications, the engine coolant temperature sensor for the radiator fan system is separate from the engine control unit.
#3. Insufficient Coolant.
If the coolant level is low, it may be pushing air into the system and the temperature sensor will not read correct coolant temperature. If the coolant level is low, you need to add coolant to reservoir.
If your coolant level is not there, you could cause your engine to overheat, which can lead to a seized engine if you’re lucky. If your engine seizes due to overheating of your coolant, it will destroy your engine and be very expensive to repair, so is something you want to be careful about.
#4. Broken Radiator Fan.
If your radiator fan isn’t working it’s probably not the relay and could be the radiator fan itself. The radiator fans have electric motors and can wear out in a few years.
You can work on testing the electric radiator fans by running a lead from the battery of your car, unplugging the radiator fan connector and running a fused 12v+ wire and ground wire into the connector.
This is the quickest and easiest way to test your radiator fans. Be careful with your hands, because they will start when you have the 12v+ wire connected.
#5. Faulty Fan Relay.
The radiator fan often draws so much current that there is a relay to power the radiator fan. Of course, the relay can malfunction, holding the radiator fan from starting.
The fan relay is often found in the engine compartment fuse box, but the best way is to look in your repair manual where it is located.
Testing a 4-pin relay is often very easy. You should remove the relay and supply 12 volts to pins 30 and 85. Ground pin 86 and check voltages coming out of pin 87. If possible, it would be better to hook pin 87 to something that draws a lot of currents; the radiator fan for example.
#6. Bad Fan Controller Module.
As mentioned before, some vehicles have a separate control module for the radiator fan control, usually in the engine compartment, where there is heat and dust. The board can then break after a while, from corrosion or other damage.
Find the relay and inspect it for visual damage on the outside. You can typically also open the relay and inspect for bad soldering or corrosion. If you see any issues, replace it.
#7. Broken Wiring or Bad connection.
If the radiator fan isn’t doing its job and the car is overheating, there could be a wiring issue or bad connection. The best thing to do is to look at the wires going to the radiator fan from the controller or relay. Also check the connection plugs for corrosion, as well pay attention to the contacts on the relay and control unit.
Using a multimeter to measure the wires, does not usually help much as you have to stress test the wires to see if they work. However, as a quick test, seeing if there is power coming to the radiator fan is easy to test with a multimeter.
How To Fix A Radiator Fan Not Coming On
To fix your radiator fan not starting, first start by checking the fuses to ensure that they are intact. The next component to check is the coolant level. You will also want to scan the codes and measure the wires with a multimeter.
For more complete information on how to fix a radiator fan that won’t start, go through the following steps:
#1. Check Fuses.
When your radiator fan is not spinning the first thing you want to do is check the fuses and replace any that are blown. There will be a large fuse for the fan itself. It will be between 30 and 50 amps and will probably be a larger fuse in the engine compartment.
However, to locate any fuse, you really need to check the owner’s manual for the location of this fuse for your car model.
Most car models will also have one or a few smaller fuses for the radiator fan control module or relay. You must also check the owner’s manual again for the exact location of the fuses for the control module or relay. Most often, you can be able to find the fuses inside the car.
If you check the fuses and find that the fuse has blown, you may want to check the wiring if you want to determine why the fuse blew. But many times a blown fuse after inspecting fuses will simply be temporary.
#2. Check Coolant Level.
Next, you’ll want to check the coolant level. Low coolant can create all sorts of issues with the radiator fan.
Checking the coolant level is simple. Open the hood and find the coolant reservoir. You’ll see a MAX sign on the reservoir, and sometimes you’ll even see a MIN sign as well.
Be sure that the engine is cold before you open whatever container houses the antifreeze, and fill the container to the maximum mark.
#3. Unplug Coolant Temperature Sensor.
You can also determine if the coolant temperature sensor is faulty by simply disconnecting the sensor. Usually, in most car models, the radiator fan will engage when the coolant temperature sensor is disconnected while the car is running.
However, you will need to find out which coolant temperature sensor controls the radiator fan because there may be a separate engine control module sensor and radiator fan control sensor.
Also, pulling the engine control module coolant temperature sensor will most likely cause a check engine light on your dash.
#4. Check Trouble Codes.
Today’s cars use a lot of technology. If the car has a problem, you almost always want to read the trouble codes from the control modules before doing anything else.
This is also a good idea if your radiator fan is not working. On a lot of car models, the radiator fan is controlled by the engine control module. If the fan is not working, you want to make sure that the ECM is aware of the problem.
If the engine control module has a trouble code stored on the coolant temperature sensor, it can also cause the radiator fan to not work correctly. In order to easily read codes, you would need an OBD2 scanner. You can buy one to use at home, or you can take your car into an auto repair shop and ask them to read the codes for you.
#5. Measure wirings.
If you have engaged in everything mentioned above and still do not know why the radiator fan is not starting, it is now time to get into some advanced diagnostics.
In order to discover what is wrong now, you will need to use a multimeter and measure the wires with a radiator fan wiring diagram for your vehicle. This can be quite difficult if you do not know vehicle diagnostics and you may want to skip this a step.
Using a multimeter, you will first need to measure the power and ground wire coming to the radiator fan. If you have power and ground to the fan when it starts, you will need to replace the radiator fan. If you are getting no power, you will next need to diagnose the fan relay and discover why it is not activating.
You could then try bridging the radiator fan relay, and if the radiator fan starts when you do that, you know there is an issue with the relay control, potentially a bad coolant temperature sensor.
#6. Talk to a professional.
The advanced electronics of modern car models can make fixing car issues challenging and there are times when it is best to have a mechanic take a look at it.
Professional mechanics have acquired thousands of hours of experience in automotive diagnostics and can identify these problems quickly.
Therefore, it is not always more expensive to have a mechanic troubleshoot the issue. Replacing parts incorrectly can be very costly as well.
FAQs.
How can I tell if my radiator fan fuse is blown?
Testing with a multimeter is the most accurate way to tell if the radiator fan fuse is defective, however, in many cases, external inspection will reveal a burnt wire inside the fuse.
What sensor controls the radiator fan?
The radiator fan is controlled by a coolant temperature sensor. There might be a separate CTS sensor for the radiator fan on some vehicles, but in most modern vehicles, the sensor used by the ECU to control the coolant is the same.
How do I turn my radiator fan on manually?
There are two ways to turn on the radiator fan. Many newer versions have a diagnostic computer that can be used for this purpose. Most of the time on older models, you can turn the radiator fan on by bridging the radiator fan relay.
How do you fix a fan relay?
If you have a faulty fan relay, it is almost always the best option to just buy a new fan relay. Often, fan relays are fairly inexpensive and if you take the chance and repair an old relay, there is a high chance the relay will fail again in the near future.
Can I drive my car if my radiator fan is not working?
No, you should not drive your car without the radiator fan working. Doing so risks overheating your engine, which could cause permanent and expensive damage to your engine.
What happens if the radiator fan is not working?
If the radiator fan isn’t working, your vehicle can get hot when it is ghosting or using low speeds, even at higher speeds, the cooling system is still cooled down by the wind. Overheating an engine can cause serious engine damage so you don’t want to take that risk.
The radiator fan system is very simple and even modern manufactured cars have something similar, so it is easy to diagnose. Typically, when you have an issue with a radiator fan, it is often something as simple as a fuse, a bad coolant temp sensor, or bad relay.
Now that you know the most common reasons, it is time to start diagnosing! I hope you enjoyed this article and now, using this information you can see what is causing the radiator fan issues.