Internal combustion engines are very inefficient. Over 60 percent of the energy produced by burning fuel becomes mostly useless heat. While you could harness a small portion to heat the cabin on cold days, the rest of the heat is a bother you have to deal with.
Every ICE vehicle needs a dedicated cooling system with efficient coolant and an equally efficient radiator.
The main heat exchanger in your cooling system is the radiator. The radiator has thousands of fins that disperse heat from the hot coolant to flowing air.
Your radiator gets this crucial airflow from natural airflow as you drive around or from an electric/mechanical fan if you are in slow traffic or parked with the engine on.
How Does the Radiator Fan Work?
A radiator fan is a big single or double fan sitting behind your radiator at the front of your truck or car.
In older cars, it is connected to the crankshaft with a belt and always spins when the engine is running. Newer cars have intelligent electric fan that only turns when the coolant temperature rises beyond a predetermined point.
- When the fan is running, it creates a strong air stream over the radiator fins
- The moving draws heat from the hot radiator and carries it away
- The process will keep on repeating hence cooling the radiator fins and the coolant better than if there was no airflow
The Case of Mechanical Radiator Fans
The mechanical fans in older vehicles were easy to maintain, troubleshoot and run. However, they put much strain on the engine since they constantly ran even when not needed.
Very few things can go wrong if you have a classic or older vehicle whose fan runs on a belt.
These are limited to:
- Broken, warped, or split fan blades
- A missing or slipping fan belt
- Damaged fan bearing
Since there are no electronics, troubleshooting such a fan is simple. A missing belt or broken fan blades are easy to spot.
A slipping fan belt will make a squeaking noise, while a damaged fan bearing will either lead to a seized fan that won’t move or a noisy fan that creaks and wobbles as it spins.
The Case of Electric Radiator Fans
If you have an electric fan, all you will get is a couple of wires delivering electricity to the fan’s motor. Moreover, you can’t just glance at the fan and conclude that it isn’t working just because you don’t see it run.
ProTip: Something as simple as loose or dirty contacts on the terminal at the fan could take it out of service. Ensure that the fun is hooked up. Clean it with a brush (the terminal and receptacle) to get rid of dust and mud before sitting it in firmly.
The fan only runs on demand. Demands vary depending on the controller setup. It could be:
- A simple thermal switch that turns the fan on when the coolant temperature rises beyond a given value
- A smart controller that factors in car speed, coolant temperature, and AC cooling setting to trigger the fan and determine actual fan speed
You will have to wait until your engine is hot enough and park the car without turning it off or spoofing a trigger signal to get the fan going.
Some of the things that could go wrong on an electric radiator fan setup are:
- Damaged wiring
- A bad temperature sensor
- Bad fan controller
- Physical damage to fan fins leaving them broken or bent
- Bad fan bearing
- A damaged fan motor
- A bad radiator fan resistor
- A bad cooling fan switch
- An unplugged radiator fan
What Happens If You Have a Bad Radiator Fan
While a bad radiator fan won’t necessarily throw an error code that lights up your check engine light, it still triggers a chain reaction that you can’t ignore. Here are the top signs and symptoms of a faulty radiator fan.
Your Engine Overheats When Idling at a Stop or Driving in Slow Traffic
The fan plays a critical role in radiator efficiency in stop and start traffic. This is because you don’t have the steady airflow you get from driving at highway speeds.
If the fan can’t kick in and suck in air, there will be little to no air movement to carry away all the heat from your radiator, making heat saturation possible.
A damaged radiator fan will lead to engine temperatures creeping up when stopped at a traffic light or stuck in a traffic jam. The temperature will immediately sink back to normal once you start driving at speed.
If you notice such a trend, have your radiator fan inspected as soon as possible. You are a few traffic jams away from ruining your engine.
Your AC Isn’t As Efficient as Before
Your AC’s heat exchanger sits next to the radiator. It uses the airflow from the fan or oncoming air when driving for efficient cooling.
Consequently, it won’t cool as well in slow traffic if the fan isn’t working. You will notice that your AC isn’t blowing cold air as it should in slow traffic, making the cabin hotter than expected.
The problem should fix itself once you start moving as natural airflow kicks in. However, if the problem persists even at highway speed, chances are your AC is out of refrigerant, the AC compressor is faulty, or there is another problem in your cooling system.
The Radiator Fan Never Comes On
If there is any electrical or mechanical damage to the fan, it will never come on, even when the engine is hot and the car is idling at a stop (or driving very slowly.)
A mechanical belt-driven fan will always be running. If you see a pulley and belt, or a pulley without a belt on your fan, it is mechanical and should be spinning as long as your engine is on.
An electric fan will only spin when the engine is hot. You can test it by:
- Take your car for a 30-minute drive
- Park at a safe spot and leave the engine idling with the air conditioning on (set to the lowest temperature possible to strain the engine more and demand more cooling from the system)
- Open the hood and monitor the fan for at least 10 minutes
- The fan should ideally kick in to help cool the car
ProTip: If the ambient temperature is very low, for instance, in winter, it might take more to warm up the engine to trigger an electric fan. This test works fastest in hot summers.
A Blown Radiator Fuse or Damaged Relay
All electric radiator fans run off a fuse. The fuse will blow if your electric fan motor or wiring is ruined and short-circuiting.
While replacing the fuse could be a quick fix, don’t keep replacing fuses if the fan keeps blowing them.
The fan motor could be shorted out, drawing extra amps, or there could be a short circuit in the wiring system.
More modern vehicles with controller modules that take in information from multiple sensors to control the fan will turn it on through a relay. If there is a relay fan in your fuse box, check that it is working.
ProTip: If your system uses a relay to turn on the fan, you can manually jump the relay to trigger the fan. This is a great way to troubleshoot the system and determine if your fan runs on demand.
Strange Whirring or Ticking Noises From the Fan
Mechanical damage on the fan will also stop it from running or make it draw more current than the system can provide.
For instance, the bearing the fan spins on could be damaged, causing loud whirring or ticking noises. The motor itself could burn out, or the brushes on the motor wear out, leading to intermittent operation.
Your radiator fan should only make a smooth whirring noise when in operation. Anything like ticking noises, wobbly operation or clanking noises hint at a problem.
Physical Damage to the Radiator Fan Fins and Structure
Finally, physical damage to the fan that ruins its structure, especially the fins, will ruin its efficiency.
Broken or torn fins mean the fan can’t move as much air as it should. Regardless of how fast it spins, it will never cool the radiator fast enough.
Replace the fan as soon as you notice any fin damage or a missing part. While it might not directly ruin your highway cruise, it will return to haunt you when stuck in a traffic jam on a hot summer afternoon.
What Could Ruin My Radiator Fan?
So, you have confirmed that your radiator fan is faulty. Even after fixing it, you have the curiosity to figure out what went wrong. Here is a list of things that could give your radiator a bad day.
Normal Tear and Wear
Every moving object in your vehicle has a definite life span. While your fan can outlast your vehicle’s warranty, it will eventually wear out – especially if it runs often.
Tear and wear could manifest in the form of:
- Damaged bearings that grind or are loose and wobbly
- Damaged motor
- Seized bearings
- Ruined internal wiring
Such eventual damage is expected in very high mileage vehicles. Nonetheless, your radiator fan is very resilient. Very few people have to replace worn-out radiator fans on their vehicles. If you do, your vehicle will be an old example, and getting a spare shouldn’t be a problem.
Front End Impact from a Fender Bender or Accident
The biggest cause of damaged radiator fans is accidents. It could be a road accident that translated force to the radiator or a tool mishap that dropped a spanner or breaker bar into a spinning fan.
The damage will either:
- Shear off a couple of radiator fan belts
- Ruin the bearing or the motor
- Completely mangle the radiator assembly and fan if it is a road accident
Water and Mud Damage – If You Offroad a Lot
While your fan can shrug off a couple of splashes, it isn’t necessarily 100% waterproof. Constantly dunking it in mud and water when offroading could mess it up, especially if the mud and water hang around the motor and bearing for a while.
Mud will not only make the fan bearing damp for longer but also make the fan heavier if it sticks on the blades.
This could push the fan’s operational torque beyond spec, leading to unnecessary strain. The same will happen if the fan spins with the vehicle still bogged down in mud or water.
You can get away with one or two instances, but veteran mud boggers will tell you water and mud, though fun, wreaks havoc on radiators and radiator fans.
Faulty Sensors and Actuators
Cars that rely on multiple sensors to turn on the fan could leave you with a dead or constantly running fan if one of the sensors reports erroneous data.
Some of the most popular sensors to check on in such a scenario are:
- Vehicle speed sensor
- Ambient temperature sensor
- Coolant temperature sensor
- AC setting system and cabin temperature sensor
You can narrow down your electric radiator fan issues to sensors or the control module if you jump the radiator fan relay and confirm that the fun runs all right when you supply 12V to it.
Rodents Chewing on the Wiring
If your vehicle has been sitting for a while and you notice any rodent nests, give the entire wiring system a thorough check.
Rodents love chewing wiring. Don’t be happy and on your merry way if the engine starts. Check all electrical systems and ensure there are no frayed or broken conductors. This will help you avoid shortcircuits and fires while making your vehicle more reliable.
Bottom Line
Your radiator fan should stand by you for hundreds of thousands of miles. However, if you notice your car overheats at low speed and cools down once you start moving, consider having the fan inspected or replaced.
Note that a dirty and clogged radiator or low coolant levels could also lead to the same problem. Have these checked after confirming that your radiator fan is working.