Radiator Fan In Your Car Not Working? Here's Why, and What to Do About It

The radiator fan in your car has a very important job to do. It is a key part of your vehicle’s cooling system, which is designed to remove the excess heat produced by the combustion process in your engine’s cylinders. If your car’s radiator fan fails and is not repaired right away, there is a real possibility that your engine could overheat, with expensive and disastrous consequences.

There can be many reasons why your vehicle’s radiator fan is not working. Fixing it can be somewhere between very simple and extremely complex. Once you understand how your radiator fan works and how to fix it, you can be back on the road with your cooling system in proper working order, ready to keep your car running smoothly!

Here’s our guide to radiator fan problems, their causes, and how to fix them.

How your radiator fan works

Your car’s radiator fan is located under the hood, directly behind the radiator. The fan’s primary function is to boost the flow of air through the radiator. The increased airflow lowers the temperature of the coolant (a combination of antifreeze and water) that flows through the cooling system. Because the engine does not always need the assistance of the radiator fan (such as when it starts from cold, is running in wintry conditions, or is cruising at highway speeds), the fan does not need to run continuously.

Depending on the type of radiator fan your car has, it may be powered by a built-in electric motor or directly by your car’s engine. Either way, it uses a thermostatically-controlled device that turns on the fan when the coolant reaches its safe maximum temperature. Once that the fan runs long enough to reduce the coolant temperature to a safe level, it is switched off until the next time that the temperature rises enough to require the use of the fan again. As you drive, the fan automatically cycles on and off as needed to keep your car’s coolant temperature within a safe operating range.

How to tell that your radiator fan isn't working properly

If your radiator fan is not coming on when it should, or staying on when it shouldn’t, there is definitely a problem. Here are a few ways to know:

• Is your temperature gauge reading very high, or has the warning light come on? (If so, shut the car off as soon as you safely can)

• Does the radiator fan stay off when you turn on your car’s air conditioning to the maximum cold setting?

• Does your radiator fan stay on all the time and never shut off?
  
  

Reasons your radiator fan isn't working

A problem in your radiator fan system can usually be traced to:

• The fuse

• The relay

• Low coolant level

• The coolant temperature sensor

• The motor, clutch, or belt

• The wiring

• The thermostat

RepairPal Tip: Tracking down the cause of a bad radiator fan, once it has progressed beyond a simple blown fuse, a bad relay, or low coolant, requires an in-depth knowledge of automotive electrical and cooling system diagnostics. If you do not have this experience, or you are otherwise uncomfortable dealing with the circuitry in your car’s electrical system, as well as very hot coolant, please contact your mechanic, who will be happy to diagnose and repair your radiator fan-related problem.

Fuse issues

Blown fuse: This is the most likely reason for a non-functioning electric radiator fan. As with many of your car’s electrically-powered systems, the radiator fan circuit incorporates a fuse. This fuse will blow in the event that its circuit is overloaded, shorts out, or has some other problem. The fuse basically gives its “life” to prevent serious damage to the fan system.

Solution: First check your owner’s manual for the location of your vehicle’s fuse box. Next, determine the location of the radiator fan fuse within the fuse box, as well as the proper rating of that fuse. With the car shut off, open the fuse box and remove the fuse for the radiator fan (use the small plastic tweezers or other tool for this task if one is provided). Now check the fuse and see if the wire inside it is broken. Also check that the fuse has the correct rating, according to the information in the owner’s manual.

If the fuse is blown, replace it with a new one of the correct rating (never install a fuse of a higher or lower rating). Close everything up, start the car, and check whether the radiator fan now works (set the A/C on full blast). If it does, you have fixed the problem! If the fan does not work, check the new fuse to be sure it has not blown. If it has blown, contact your mechanic for repairs. If the fuse is OK, but the fan does not work, keep reading…

Relay issues

Bad relay: The relay for the radiator fan system is also found in the fuse box. The radiator fan relay controls the delivery of power to the fan itself. A bad relay will prevent the fan from working properly. If the relay is bad, you might hear a clicking sound coming from the relay when the fan tries to turn on.

Solution: Look in your owner’s manual for the location of the relays, which are often part of the main fuse box. Identify where the radiator fan relay is located. With the car’s power off, find the relay and remove it.

If there is another relay of identical specifications and rating, you can try to switch that one with the fan relay. If not, you will need to buy a replacement relay and install it. Now start the car and activate the fan (by putting the air conditioning on the maximum cold setting) – if it works, you have solved your fan problem. If you had an identical relay to switch around, put it back in its original location and buy a replacement relay for the fan circuit. Insert it, close everything up, and you are good to go. If you still have a problem, try the next possibility…

Low coolant level issues

Insufficient coolant: If your car’s coolant gets too low, there will not be enough coolant in your cooling system to properly remove the heat produced by your engine. Additionally, a low coolant level can allow air to circulate along with the coolant, further impairing cooling efficiency. Catastrophic engine failure can be the outcome. You may notice that your temperature gauge is running high or that you are seeing a low-coolant or engine overheating warning lamp light up on your dashboard.

Solution: If you see any of these signs while you are driving, pull over safely as soon as possible and shut off your car. Wait until the vehicle cools down completely, then open the hood and check the coolant level on the translucent reservoir (check your owner’s manual for its precise location). The level should be somewhere between the “MIN” and the “MAX” marked on the reservoir. If the level is below the “MIN” mark, add enough coolant to fill it to the “MAX” mark.

Be sure to use coolant that is approved for your vehicle and diluted to a 50/50 antifreeze/water blend. Start your car with the hood still open and watch to see whether the coolant level drops any further. If it does, this may be the excess air working its way out of the system. Shut off the car and add enough coolant to return the level to the “MAX” mark. Start it up once more and check for any coolant leaks from the reservoir, the radiator, the coolant hoses, and underneath the car. If the coolant level is stable, the warning lights are off, the temperature gauge reads normal, and there are no coolant leaks, you should be OK to continue driving. If you still have a problem, contact your mechanic right away.

Coolant temperature sensor issues

Bad sensor: The coolant temperature sensor (CTS) is the device that sends a signal that the radiator fan needs to come on, based on the temperature of the coolant that is circulating through your engine. The CTS can either be built into the engine control computer or it may be a separate module. If the CTS is bad, the fan will not turn on to cool your engine when it should. The result could be engine overheating. Other symptoms can include poor fuel economy, black exhaust smoke, or illumination of the Check Engine Light (CEL) on your instrument panel.

Solution: This is a job for your mechanic, who can troubleshoot the CTS to determine whether it is working properly. If not, it can be replaced relatively inexpensively.

Fan motor, clutch or belt issues

Bad fan components: Your car’s radiator fan is essentially not too different from a household motorized fan, in which a motor drives a fan blade to provide a cooling effect. While many radiator fans use thermostatically-controlled electric motors, others are driven by the car’s engine. Older vehicles have fans that are driven by an engine-mounted belt and run continuously. Newer vehicles with engine-driven fans incorporate a clutch that connects the fan when it is needed for engine cooling and disconnects when it is not needed. What this means is that a problem with the fan itself can involve:

• The motor on an electrically-powered fan

• The fan belt on an older vehicle

• The fan belt and/or clutch on a newer vehicle with an engine-driven fan

Whatever type of fan your vehicle has, if it stops working, your engine will not get adequate cooling.

Solution: Your mechanic can determine the exact type of motor, clutch, or belt-related fan repair that you need and take care of it for you. A straight fan belt replacement will be the least expensive option, followed by replacing the electric fan motor, and then doing the fan clutch (which is often combined with the water pump assembly). Once repairs are made your car should run normally.

Wiring issues

Bad wiring: Because your radiator fan system uses motors, fuses, and relays that are controlled from your engine’s computer, there is plenty of wiring needed to connect all of these components together. Any damaged, broken, or disconnected wiring can keep your radiator fan from working when it needs to, threatening the health of your engine should it overheat.

Solution: Your mechanic can troubleshoot your radiator fan’s wiring system, look for any wiring faults, and repair them as needed.

Thermostat issues

Bad thermostat: Your engine’s thermostat is a temperature-controlled valve that opens and closes to allow coolant to flow through your cooling system. Over time, the thermostat can fail and stick in either the open or closed position. When this happens, your engine can either run too cool (if it sticks open) or run too hot and overheat (if it sticks closed).

Solution: While the thermostat is not strictly a part of the radiator fan system, a bad one can definitely cause problems for your cooling system. Depending on the symptoms your car is displaying, your mechanic may want to check the thermostat and rule it in or out as a cause. Replacing your thermostat, if necessary, can be done at a reasonable cost.

Can I drive without a radiator fan?

Absolutely not! Driving for any prolonged period without an operating radiator fan is very likely to overheat your engine and result in an extremely expensive engine repair bill. This means that having your car towed to your mechanic is the smart move, once you are aware that you have this type of problem. It’s just not worth risking a catastrophic engine failure. If you have any questions, contact your mechanic right away – and don’t drive your car until you do!