Your car’s cooling fan, or radiator fan, plays an important job in keeping your engine cool.
Some of the most common causes of a faulty radiator fan include a blown fuse, a faulty temperature sensor, or a defective fan relay. If the fan stops working, your engine could overheat and be damaged.
Below, we’ll explain how you can tell if your cooling fan isn’t working and what you can do about it.
How does a car’s cooling fan, or radiator fan work?
If you’ve ever wondered “What does a car radiator fan do?”, we’ll explain in detail on this page.
When you're driving, air flows through the car radiator to keep your engine at a normal temperature. But if you stop, for example in a traffic jam, modern cars use an electric cooling fan to force air through the radiator.
This fan is usually located at the front of your vehicle, either just in front of the radiator or just behind it. Your cooling fan will usually be inactive, but if your car is stationary (with the engine running) or the temperature starts rising, it will kick into action.
Your car’s cooling fan can be activated in one of two ways:
- The internal thermostat (part of the car’s cooling system) senses that the radiator is getting too hot.
- When the sensors in the cooling system of your car detect that the coolant is getting too hot, the electrical systems will automatically switch on the cooling fan via a relay switch which is activated by the engine management system.
As one of the top ten breakdown causes (overheating), it’s important to keep your cooling fan in top shape.
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How do I know if the car radiator fan isn’t working?
Many modern cars don't have a temperature gauge, but there'll be a light to tell you if the engine's overheating.
If a red or yellow temperature icon lights up on your dashboard, you should stop as soon as it’s safe to do so. You might also see a warning message on the dashboard display.
A yellow light probably means that the coolant level is low. A red light means that your engine's overheating.
What happens if the radiator fan stops working?
If your radiator fan is not working, your engine could overheat. This could cause damage to your engine parts. If ignored, this could result in your car coming to a complete stop when the engine is no longer able to keep going without sufficient cooling in the vehicle. In the worst case, you could be on a motorway and cause an accident.
It’s a serious issue and needs to be looked at by a garage.
Can a car run without a cooling fan?
Modern cars may be better equipped to run for a while if the cooling fan fails – this is because they are designed with multiple systems in place to assist cooling (usually with an electric pump that can continue to circulate air in the event of a cooling fan failure). Even with a modern car, you should get your radiator fan looked at ASAP if there’s a problem with it.
With older cars, you shouldn’t risk driving on if there’s a problem with the cooling fan. They aren’t designed to have fallback systems in place to help with airflow, so fan problems are serious. Get your car looked at by a professional or get it taken to a garage immediately.
What's wrong with my car’s cooling fan?
In most cases, a problem with your cooling fan can be fairly serious, so it’s best not to chance it – always get your car checked over.
Your mechanic will look for one of these common cooling fan faults:
Blown fuse
As the radiator fan is electrical, the problem could be with the fuse.
Your car’s manual should show where the fuse for the cooling system is. If the fuse has blown, the mechanic will need to replace it and check the operation of the fan right away.
Car radiator leak
If you have a car radiator leak, your car radiator sealant may have failed or peeled away entirely in places, causing the all-important coolant to leak out. Signs that you have a radiator leak include:
- You can see radiator fluid leaking underneath the car
- The radiator is making a hissing noise
- The radiator looks rusty
- The coolant level has dropped rapidly
- Your car is hot but the radiator is cool (do not check this yourself, as there’s a risk of getting burnt)
Faulty temperature sensor
On most modern cars, the cooling fan is controlled by the Engine Control Unit (ECU) which gets a signal from the coolant temperature sensor.
If it’s not working, the fan won’t turn on when it needs to, which means the engine might overheat.
Defective fan relay
The fan relay controls the power to the cooling fan (and the cooling fan relay switch). If there’s an issue with the relay, the fan will be affected.
It may cause the fan to cut in and out, or not come on at all.
A wiring issue
Faulty car wiring could be to blame. The mechanic will check to see if all the wires to the fan are properly connected and in working order.
Something wrong with the fan motor
If the motor that drives the fan is faulty, then a new motor will have to be fitted.
Coolant level low
Check the engine coolant level. If your engine coolant’s too low, it means that the cooling fan will have to work harder to keep the engine at a normal temperature.
To check the level, look for the coolant expansion tank in the engine bay. There are usually two marks on it – a minimum and maximum level mark. The coolant level should always be between these 2 marks.
What should I do if my cooling fan breaks?
If the red or yellow temperature light comes on, you need to:
- Pull over as soon as it’s safe to do so.
- Turn the engine off.
- Get your car checked by a garage or contact us for help.
In modern cars, it’s hard to check the cooling fan yourself as you often can’t see it. And if it has stopped working, you’ll need a professional to repair it for you.
That’s why it’s best to take your car to a garage. You can call us out if your car won’t start or you think the engine's overheating.
How do I fix my car fan that’s not working?
Unless you’re a fully trained mechanic/you run your own garage, you shouldn’t attempt any repairs with a faulty car fan. Get it checked by a professional. It may be off-putting to think about the cost of getting it fixed by someone else, especially if you don’t have breakdown cover, but it’ll be worth it in the long run. Attempting a fix by yourself may result in mistakes which could lead to even bigger problems with your vehicle.
Car fan coming on after a short journey
It’s not always a problem when your car fan comes on after a short journey, as it may just be due to exceptionally hot weather outside. However, this can also indicate a problem with the cooling system – your car may be low on coolant or there may be a malfunction with the electrical systems (like the relay or a short circuit in the fan).
Your car fan coming on after a short journey could also be due to you keeping you’re A/C running. In any case, it’s best to get your car checked over by a mechanic, just incase.
Cooling fan comes on when car is cold
If your car’s cooling fan comes on when it’s cold, this could be a result of the cooling system’s thermostat being stuck in a closed position, a problem with the cooling fan relay, or a damaged temperature sensor.
Why is my car’s cooling fan so loud?
If you can hear your car’s cooling fan and it’s much louder than usual, this could be due to several reasons:
- There’s a build up of debris within your fan (dust etc.)
- The blades of the fan are bent or damaged, causing them to catch on other pieces of the cooling system
- The bearings are worn out or the rotating assemblies are unbalanced
How much does it cost to replace a cooling fan in a car?
If you're getting a cooling fan replaced and you don't have Parts & Garage cover, the one-off price at a garage could range anywhere from £100-£500+ depending on the scale of the problem.
How do I know when my car radiator fan needs replacing?
There are a few really obvious ways to tell if your car’s radiator fan needs replacing:
- The engine overheating warning light comes on (this looks like a red or yellow temperature symbol)
- You can see steam coming out from under the bonnet of your car, or a leak from underneath your car
- Your car's temperature gauge is reading much higher than usual, especially when stuck in traffic
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