When the temperature starts to rise, the fan has to work
Summer, city traffic, the air-con on full, and the temperature needle creeps slowly but surely toward the red zone. Sound familiar? The electric radiator fan is the hero that saves your engine from overheating in moments like these. While you drive fast enough, airflow through the radiator is enough to cool the engine. But in city driving, at a traffic light, or in a traffic jam, the only thing cooling the radiator is the electric fan.
When the fan stops working, the engine overheats. And engine overheating is one of the most expensive faults that can happen to you. A warped cylinder head, a blown head gasket, damaged pistons ... all that can be a consequence of overheating. And all of it costs hundreds or thousands of euros to repair.
That is why a working radiator fan is absolutely essential. And when it fails, a used fan can be an excellent solution.
How the cooling system with an electric fan works
The cooling system of a modern car has a few key components:
- Radiator - a large heat exchanger at the front of the car through which coolant flows
- Water pump - circulates coolant between the engine and the radiator
- Thermostat - regulates coolant flow depending on engine temperature
- Electric fan - boosts airflow through the radiator when natural flow is not enough
- Temperature sensor - measures coolant temperature and sends the data to the ECU
- Fan relay - an electronic switch that turns the fan on and off
When the coolant temperature reaches a set value (usually around 95 to 100 degrees Celsius), the ECU triggers the relay that turns on the electric fan. On some cars the fan has two or even three speeds, depending on how much cooling is needed.
Many modern cars have two fans: one for the engine radiator and one for the air-conditioning condenser. Sometimes they work together, sometimes independently, depending on the need.
Why electric fans fail
The electric radiator fan is a fairly simple device: an electric motor with blades. But there are a few reasons why it fails:
Worn motor bearings - over time, the bearings in the electric motor wear out. The fan starts to hum, slows down, and eventually stops completely. This is the most common cause of failure and usually happens gradually.
Burned-out windings - if the fan runs too long under full load (e.g. due to a clogged radiator or low coolant level), the motor windings can overheat and burn out.
Worn brushes - on fans with a brushed motor, the brushes wear down and lose contact. The fan starts to run intermittently or not at all.
Damaged blades - cracks or damage to the blades reduce airflow and create vibrations that add load to the bearings.
Connector corrosion - the fan connector is exposed to moisture and dirt. Corrosion on the contacts creates resistance that reduces motor power or breaks the circuit completely.
Faulty relay or fuse - before you conclude that the fan is broken, check the relay and fuse. They are much cheaper parts and a common cause of the problem.
How to spot a faulty fan
Here are the symptoms you should watch for:
The engine overheats in city driving - if the temperature rises while you are stuck in traffic but normalises when you drive on the open road, the fan is the most likely culprit.
The fan does not run when the air-con is on - the air-conditioning needs the fan to cool the condenser. If the fan does not run with the air-con on, the engine will overheat quickly.
Unusual noises - humming, squealing or knocking from the radiator area when the fan is on. Those are signs of worn bearings or damaged blades.
The fan runs all the time - if the fan runs non-stop even when the engine is cold, the problem is not in the fan but in the temperature sensor or relay. But that constant load can quickly destroy an otherwise healthy fan.
The fan spins slowly - if the fan runs but is clearly slower than before, the bearings are near the end of their life or the brushes are not making good contact.
Why buy a used fan
A new electric radiator fan costs 100 to 400 euros, depending on the car make and model. For some cars with twin fans or more complex systems, the price can climb to 600 euros.
A used fan usually costs 30 to 100 euros. That is a saving of 70 percent or more. And given that the fan is a fairly simple device, a used unit with low mileage can serve as well as a new one.
It makes particular sense for:
- Older cars where a new fan costs disproportionately much compared to the car's value
- Cars with two fans, because replacing both with new ones can get very expensive
- Situations where the fan is mechanically sound but has a damaged blade, since you are buying the whole assembly
How to test a used fan before buying
Testing a fan is luckily very simple:
Battery test
Connect the fan directly to a battery (12V). Positive terminal to the fan's positive lead, negative to negative (or to the housing). The fan should spin up strongly straight away. Listen to the sounds: it must run smoothly, without grinding, knocking or humming.
Visual check
Look at the blades. They must have no cracks or missing pieces. Check the shroud that holds the fan, it must not be cracked or the fan will not sit properly in front of the radiator.
Bearing test
When the fan is off, try to spin the blades by hand. They should turn smoothly and freely. If you feel resistance, scraping or squealing, the bearings are worn. Also try to move the shaft up and down. If there is play, the bearings are bad.
Connector check
The connector must be clean, free of corrosion and with undamaged contacts. A corroded connector can cause intermittent fan operation or a complete stop.
Fitting a used fan
Replacing the electric fan is a fairly simple job on most cars:
- Disconnect the battery
- Unplug the fan's electrical connector
- Undo the bolts that hold the fan shroud on the radiator (usually 2 to 4 bolts)
- Lift out the old fan together with the shroud
- Fit the used fan in reverse order
- Reconnect the connector and the battery
- Test it by turning on the air-con or waiting for the engine to warm up
On some cars, access to the fan is restricted by the position of other components (e.g. intake manifold, air-con radiator), so it may take a bit more time and tools.
If you are buying only the fan motor without the shroud, check that it is compatible with your existing shroud. The diameter and the mounting bolt pattern must match.
Multi-speed and PWM-controlled fans
Older cars have simple fans with one or two speeds (low/high), controlled by relays and resistors. Newer cars use PWM (Pulse Width Modulation) controlled fans that can run at any speed from 0 to 100 percent.
PWM fans are quieter and more energy-efficient, but they are also more expensive. When buying used, make sure to check which type your car uses and buy the matching one. A PWM fan will not work on a car that expects a classic on/off fan, and vice versa.
Preventive maintenance
Here is how to extend the life of the fan, whether new or used:
- Check the coolant level regularly. A low level means the engine heats up faster, and the fan has to run longer and harder.
- Clean the radiator of leaves, insects and dirt. A clogged radiator reduces cooling efficiency and loads the fan.
- Replace the thermostat when it starts to fail. A thermostat that stays closed causes overheating and excessive fan work.
- Check the condition of the coolant. Old coolant loses its properties and removes heat less efficiently.
Where to find a used fan
On the PoDi platform you can send a request for a used radiator fan. State the make, model, year and engine type, and suppliers will send you offers. Try to find the complete assembly (motor + blades + shroud) because it is the simplest to fit and removes compatibility problems between components from different makers.
The electric radiator fan is a part that buys very well used. It is easy to test, durable, and the price gap between new and used is significant. If your fan is showing signs of dying, do not wait for it to leave you stranded mid-summer in a traffic jam. Get a replacement in time and enjoy safe driving without the fear of overheating.