Troubleshooting Electric Cooling Fan Problems in Cars - AxleAddict - A community of car lovers, enthusiasts, and mechanics sharing our auto advice
Updated date:

Troubleshooting Electric Cooling Fan Problems in Cars

Dan Ferrell writes about do-it-yourself car maintenance and repair. He has certifications in automation and control technology.

Testing a failed cooling fan circuit can be tricky at times.

Testing a failed cooling fan circuit can be tricky at times.

Cooling fan problems can be hard to diagnose, depending on your vehicle model and the type of failure. Still, you can avoid much of the confusion using a troubleshooting plan.

If your electric radiator fan isn't coming on after the engine reaches operating temperature—the key here is operating temperature (more on this later)—you can bet there's something wrong with the fan assembly itself, the circuit, or one of its components.

This guide walks you through some of the most common electric cooling fan problems to help you troubleshoot and identify the problem when the fan refuses to work, or works intermittently.

On older vehicle models, the fan circuit is simple, and you may not have trouble locating operating components or the fault itself.

Modern vehicles use the electronic control module (ECM-car computer), powertrain control module (PCM), or a dedicated fan control module (or both) to control the operation of the radiator fan, and can be little more complicated to troubleshoot sometimes.

So, with newer vehicle models, it's a good idea to have the vehicle repair manual for your particular make and model on hand, especially with fairly recent models. The manual explains the operation of the cooling system, how your cooling fan operates, and the sensors or switches your car computer reads from to operate the cooling fan. Besides, the manual can help you locate sensors, relays, switches and trace circuit wires as necessary. Haynes makes good aftermarket manuals.

If your engine is overheating and you suspect problems with the cooling fan, this guide gives you important troubleshooting tips, and the steps to diagnose the most common cooling fan failures you are likely to encounter on your car.

If your cooling fan runs continuously, check the fan relay or cooling fan temperature switch, or engine coolant temperature (ECT) sensor.

Before going into the necessary steps to troubleshoot the fan in your vehicle, though, a brief fan operation description follows.

In This Article:

Cooling Fan Operation

Troubleshooting Shortcuts

Cooling Fan Troubleshooting

  1. Has Your Cooling Fan Actually Failed?
  2. How to Test the Cooling Fan Motor
  3. Checking Wires, Connectors and Related Components
  4. Testing the Cooling Fan Temperature Switch
  5. Testing a Cooling Fan Relay
Cooling fan helps control engine and other components temperature in the engine compartment.

Cooling fan helps control engine and other components temperature in the engine compartment.

How the Cooling Fan Works

If the cooling system in your vehicle uses an electric cooling fan, most likely you have a transversal (sideways) mounted engine. However, some longitudinal (front to rear) mounted engines use the electric fan as well, but they usually have an engine-powered cooling fan.

The electric cooling fan uses a direct current (DC) electric motor with a thermo switch, module or computer control to turn it on or off, depending on coolant temperature or AC operating condition.

On older fan circuits, the thermostatic switch connects to battery power on one side, and to the fan motor on the other. However, on most '90s and newer models the control was passed to the car computer or a dedicated module. For example, when coolant temperature changes, the thermo switch reports this change to the computer through a voltage signal, which the computer or module uses to activate the cooling fan through a fan relay(s).

An electric cooling fan not only helps save energy by running only when the system needs to remove excess heat away from the engine, but helps shield other sensitive circuits and electronic components from heat damage. During the winter months, your radiator fan saves even more energy when enough cool air flows through the radiator on the highway.

Even if your cooling fan doesn't have a complicated circuit, you still need to know where to look when your fan doesn't work as expected. Next are some fan circuit key points you need to check when diagnosing problems with your electric cooling fan.

Some Troubleshooting Shortcuts

1. If you think the cooling fan isn't working because your temperature gauge is indicating overheating, open the hood, start the engine, and let it idle for 15 to 20 minutes. If the fan comes on, you may have a bad temperature sensor or gauge.

2. A cooling fan temperature switch (or sensor, in some vehicles) can also get stuck, which may cause the fan to run continuously any time you turn the ignition key on or start the engine. Troubleshoot the switch.

3. On some modern vehicles, an ambient air temperature sensor, vehicle speed sensor, and other sensors may provide input to the car computer to determine radiator fan operation. Consult your vehicle repair manual to check the required sensors and switches.


On a warm engine, the fan may come on even if the engine is not running. When working on a hot engine or an engine that is running, keep your hands and tools away from the fan blades and moving components.

Locate cooling fan circuit components.

Locate cooling fan circuit components.

Troubleshooting Your Cooling Fan

Troubleshooting a cooling fan that doesn't work can be a relatively straightforward task at times. Usually, the problem resides with the fan motor itself, a thermo switch, relay, wire, or (less commonly) the computer or module itself.

1.Has the Cooling Fan Actually Failed?

On many modern vehicles, if you want to confirm whether your cooling fan is in working order, you can start the engine and let it idle. Set your air conditioning to the MAX setting and turn it on. The cooling fan should come on immediately or within the next couple of minutes. On older vehicle models, just wait about 15 to 20 minutes for the engine to reach operating temperature. Then, the fan should come on.

  • If the fan comes on when the AC is running at MAX, but doesn't run when the engine is hot, check the temperature sensor or switch that sends the signal to the computer or module to operate the fan. On modern vehicles, a bad sensor usually triggers the check engine light. Scan the computer for trouble codes, if necessary.
  • If the fan fails to come on, first check for a fan blown fuse or triggered breaker. On older vehicle models, you may have a fusible link in the circuit. This is a piece of wire inside an insulated block of rubber. You won't miss it. Grab the ends of the fusible link and try to stretch it. If it stretches, the wire link might be broken. Replace it.

CAUTION: If the fan fuse or fusible link is blown, or the breaker has been triggered, it is possible the fan motor itself may be bad and causing the fuses to blow. Replace the fuse or fusible link, or reset the breaker, and test the fan motor again. If the same problem appears and there's no wire causing a short circuit, replace the fan motor.

NOTE: if the cooling fan doesn't come on when the engine has been operating for 20 minutes or more, make sure that coolant is reaching operating temperature, around 220°F (104°C). You may be dealing with a stuck-open thermostat. Check the temperature of the engine block and radiator tank (the one that connects to the engine with the upper radiator hose) using a kitchen thermometer. Make sure that engine temperature reaches about 220°F (104°C) and the radiator tank temperature rises accordingly (meaning hot coolant is being transferred to the radiator). If temperature remains fairly steady around 200°F (93°C) or less, the temperature switch or sensor may fail to trigger the radiator fan on.

Connect fan directly to power for testing.

Connect fan directly to power for testing.

2. How to Test the Cooling Fan Motor

If the fan fails to come on, you still can check the fan by connecting direct battery power to it (while working and making tests in the proximity of the fan, always stay clear and keep tools away from the fan).

1. Unplug the fan wiring connector. Closely examine the connector for corrosion or damage. If necessary, use electrical contact cleaner to clean the connector. Make sure the wires are firmly attached to the connector and not damaged.

2. Look at the polarity of the wires leading to the fan, identify power and ground (usually a black wire).

3. Using jumping wires, connect battery negative to the ground side of the fan connector and positive battery to the other wire. On some vehicles, the fan connector comes with three terminals, two for power (high and low speed, test both) and another for ground. Or you may have a four-wire terminal (high and low speed and two grounds, test each pair separately). Consult your vehicle repair manual to identify each wire, if necessary.

4. Once you connect the fan to battery power, your fan should start running.

  • If the fan doesn't work with direct battery power, examine the terminal that plugs to the radiator fan connector. Look for corrosion and damage. Then test for incoming voltage at the terminal with your digital multimeter (DMM). With the engine running and at operating temperature, touch the terminal positive and ground with the respective multimeter probes, you should get running voltage (about 14V), indicating the fan should be running. If your test proves incoming power, replace the fan motor.
  • Check for any blown fuses or a tripping breaker. If your find a circuit blown fuse or tripped breaker, the fan motor might be pulling too much voltage, causing the fault. Check for a shorted wire or replace the fan motor.
  • If the fan doesn't come on at all, or runs noisy or at an abnormally low speed, replace the fan motor.

Still, on some vehicle models, you can unplug the single wire connector from the coolant temperature switch to trigger the cooling fan on, or by grounding the wire using a jumper wire while the vehicle is running. Just keep in mind that your computer may set a trouble code for a malfunctioning temperature switch

The video at the bottom of this post gives you a visual guide to troubleshoot the temperature sensor and fan motor.

3. Checking Wires, Connectors and Related Components

If the cooling fan motor and fuses, breakers or fusible links seem to be in working order, it's time to check the circuit and related components. You may need to consult your vehicle repair manual to locate components and wires in the circuit.

Try to follow the fan wires back to the coolant temperature switch or cooling fan relay on modern vehicles. Closely examine the wires for cuts or damage.

Sensor(s) in the cooling fan circuit handles the signal to turn on the cooling fan.

Sensor(s) in the cooling fan circuit handles the signal to turn on the cooling fan.

4. Testing the Cooling Fan Temperature Switch

Consult your vehicle repair manual to locate the switch, if necessary. On most modern vehicles (late '90s and newer), you are looking for the switch that connects to your car computer (powertrain computer), since there may be more than one switch.

You can test the cooling fan temperature switch using a test light.

1. Connect your test light to battery ground.

2. Start and idle the engine, and backprobe the connector terminals with the test light. One of them should turn on the test light.

3. Wait for the engine to reach operating temperature.

4. Now backprobe the other wire at the connector. Your test light should come on. Otherwise, the switch is not working.

NOTE: If your vehicle repair manual gives you the cold and hot Ohms (resistance) values for your temperature switch, you can test it with a digital multimeter. Test switch resistance with the engine cold, and after idling the engine for 15 minutes. Turn off the engine and test again. Compare values to the ones on your manual. If you don't have the cold and hot values for your switch, you still may want to test the switch and compare the difference in values. This will tell you the switch is still working somehow.

Also, on newer vehicles the coolant temperature sensor operates the A/C and the cooling fan. If your vehicle repair manual gives the Ohms values at cold and hot condition, use your voltmeter to test the temperature sensor, if necessary. If you don't have the sensor's resistance values but you notice that Ohms remains pretty much the same at cold and hot, replace the sensor.

Test the fan relay for operation.

Test the fan relay for operation.

5. Testing a Cooling Fan Relay

  • The easiest way to know whether your relay is causing trouble is to replace it with another relay in your vehicle you know is working fine. Look at the power center under the hood for a similar relay that won't interfere with the correct operation of your engine if swapped, like a window or wiper relay.
  • If you can't find a suitable relay, you still can test the relay. Go ahead and read the steps described in How to Test a Fuel Pump Relay. The steps are the same for your relay. Most fan relays come in one of three different configurations. Make sure to correctly identify the prong terminals on your relay. See the schematic printed on the relay itself or consult the schematic in your vehicle repair manual, if necessary. The schematic will help you also when checking the fan cooling circuit.
  • If swapping relays still doesn't operate your cooling fan, make sure the relay is receiving power from the computer.
  • Consult your repair manual to identify the wire that sends power to the relay. Usually, there's power to the relay even if the engine is off. You can use a test light to check for power here. Connect the test light wire to a good ground and probe the power terminal on the relay socket. Turn the ignition key to On, if necessary. The test light should come on. If there's no power, there may be a fusible connector hooked to the power wire that is at fault, or the computer is not sending power to the relay. Consult the circuit schematic on your repair manual to follow the wire back and keep checking for voltage as necessary.
  • If the relay is working, check the wire(s) and fan connector for damage.

When checking for cooling fan problems, make sure the fan shroud and other original equipment aim to improve air flow around the engine in in place. Missing equipment can greatly reduce a radiator fan efficiency.

Many modern vehicle models have a much more complex cooling fan circuit that the ones described here. Refer to your vehicle repair manual to locate wires, components, and modules, if necessary. Still, in some cases, you need to make a diagnosis using a professional scan tool to check for voltage values and power inputs to the cooling fan to locate the source of the problem.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

Questions & Answers

Question: My cooling fan is not working on overheating, but it works with A/C. Why is this?

Answer: You may want to check the coolant temperature sensor.

Question: My 2008 BMW 750i has 12 volts to the connector, even when the switch is off. What controls this?

Answer: There could be a short in the circuit. It's possible the problem is with the temperature sender or the wire, which may supply the ground for the relay. You'll need a wiring diagram to trace the voltage back and check this, though.

Question: My car is a 2012 Toyota Ractis model. My cooling fan is not working properly while AC running and AC is not cool. Why?

Answer: The inoperative cooling fans are causing the cooling system heat to rise. That’s why your AC is not cool. Had the AC system checked. It could be low on refrigerant or a bad relay, a sensor, an ambient temperature switch or the AC pressure transducer is bad.

Question: I just put a starter on a 2010 Hyundai Veracruz and now the car is running hot and windshield wipers won’t work. Why would it be running hot ?

Answer: There could be many reasons why an engine may be running hot. If the problem started right after replacing the starter, check for a blown fuse. The wipers issue may or may not be related to the problem. This other post may help:

Question: My aux fan is not working, how should I fix it?

Answer: Check first the fuses and relays for the fan's circuit. You may need the diagram for your model. There could be a wire that's not getting current behind the dash between the AC and cluster.

Question: Why would my cooling fan not be working on my 2005 Mitsubishi?

Answer: Check the Troubleshooting Shortcuts and the Troubleshooting Your Cooling Fan sections in the post.

Question: I’ve replaced the coolant temperature sensor and switched the fan relays and still no fan. I know my fan works cause when I unplugged the sensor it came on. What could be the problem with my electric cooling fan?

Answer: Usually, the problem is with the fan control module. Check for trouble codes, even if the check engine light is not on. On rare cases, the problem is traced back to the car’s computer.

Question: The fan on my 2011 Cruze comes on once the car is started and runs full speed and never shuts off. It seems like my car has no heat as well. Any ideas what the problem could be?

Answer: Check the relays and the coolant temperature sensor. There might be a short in the circuit.

Question: On my 2008 Toyota Highlander, the cooling fan comes up for about a minute and then goes off (mostly at night) without the engine being on and often runs the battery down. What could be the cause of the cause, please?

Answer: The fan coming on with the engine off is normal in modern vehicles. But check the battery, there could be a bad cell, causing a discharge.

Question: The fan on my car started to turn on too often. It is the same temperature outside, and we are in the middle of mild winter. I am not running aircon at the moment, no need. Is something on its way?

Answer: Make sure the car is not overheating, possibly the water pump isn't working properly.

Question: My 2006 G35 is not overheating, but when the car gets up to operating temperature, both fans come on high and do not turn off until I shut the car off. What should I look into to remedy this?

Answer: Check the coolant fan relay and coolant temperature sensor.

Question: Will a car overheat on a long distance trip with no cooling fan?

Answer: There might not be enough air flow through the radiator to the engine, depending on your model and the location of the condenser.

Question: I am experiencing a short on the condenser or cooling fan. What could be the problem? How do I fix this?

Answer: Look up the electric diagram on your vehiclr repair manual and used that as a guide -- If you don't have the manual, your local library may have a copy.

Question: What would cause my cooling fans to stay on even when the vehicle is cold?

Answer: Unplug the cooling temperature sensor. If the fan stops, replace the sensor.

Question: I have a 1995 Ford Taurus GL Station Wagon. The temperature used to run about the middle of normal. Recently it rose to the L in normal and I had flushed the system, changed both temperature sensors and the control module over the center of the radiator, the radiator fan and the circuit breaker to the fan. I replaced the radiator about 3 months earlier. The only other thing I never replaced is the water pump?

Answer: If the thermostat is old, you may want to replace it as well. You can listen to the water pump with a length of hose and see if the bearing or noises come from it. The impeller may be loose. Check the belt that runs the pump. That can also be a problem. Although not that common, the temperature gauge may also become faulty.

Question: My 1995 Accord’s fan only runs after I shut the motor off. I’ve replaced the fan timing unit, switch, thermostat, and tried swapping relays and topped it off after bleeding the coolant system. What do I do next?

Answer: Maybe there's a problem with the thermocouple sensor. But you need to have the diagram for the circuit and follow the voltage to see where is or isn't going.

Question: Why is my car's cooling fan still on after I turn my car off?

Answer: It is normal for the cooling fan to stay on, it helps the engine to cool. Most modern vehicles has this configuration.

Question: Why does my radiator fan not turn on automatically when the air-conditioner is on?

Answer: Check that you still have refrigerant in the system. If it's an old system, there could be a leak as well.

Question: My cooling fan is staying on all the time in my 2002 Lincoln Town car. The battery is also dead. When I hooked up the booster, the fan started. What could be the problem?

Answer: Usually, this is caused by a bad cooling temperature sensor. Try unplugging the sensor and see if the fan stops. If it does, replace it. Another problem could be a grounded wire or stuck relay. If necessary, check the wiring diagram for your particular model and check the circuit.

Question: I have 2003 Toyota corolla. I perceive a kind of gaseous odor while the ac is cooling. It doesn't happen all the time. What could be the problem?

Answer: There could be several reasons for this. Some of the most common reasons for this type of odors come from a dirty, cabin air filter, mildew in the passageways (vents, evaporator); engine leaks can also produce this type of smell.

Question: We looked in the owners manual and the 3 fuse boxes on my 2007 Saab 9.3 2.0T sedan. None of these tell us which is for the radiator fan so we can’t check it. How can we locate this fuse?

Answer: I don’t know if these are the right ones for your model. But check the F35 fuse (I think is a 40 amp) and Maxi fuse 36 (engine bay box), and fan relay (don’t know exactly where it’s located). Also, you may want to check out this page and test the cooling sensor as described. Hope this helps.

Question: My 95 Cadillac DeVille, when I unplug the relay, the fuse blows to the engine coolant sensor. What is wrong?

Answer: Check for a short in the circuit, probably around the relays area.

Question: On a Toyota RAV4, the fan comes on as soon as you switch ignition key on. What could be wrong?

Answer: There could be an open in the temperature circuit sensor. The Rev 4 might have the sensor at the bottom tank of the radiator. If the sensor is plugged in, test the sensor and/or the wires. Also, it's possible the fan relay is stuck. You may need to test the relay:

Question: I have a Chevrolet Aveo LT 2008. The fan is not turning on low speed if the engine is on, even if it reaches the heat indicated. But if you turn on the A/C, it will come on. What could cause my Chevrolet's fan to only turn on with the A/C?

Answer: Check the engine coolant sensor and the relay for the low-speed circuit. There could be the problem.

Question: I have Honda Accord 2003. It has an electric radiator fan. The car has never overheated but I feel the radiator fan never comes on. Is this possible?

Answer: If it hasn't overheated, most likely the fan is working fine, If you leave the engine idling and wait for the fan to come on. it usually takes about 15 to 20 minutes.

Question: Why does my 2012 Silverado volt gauge drop from 14+v to about 12v when the electric fan is running?

Answer: Electric fans draw quite a bit of amperage and it's possible for some alternators to lack a sense of such high draw if it is not designed for it. Still the alternator should be putting out over 13 volts, even if your meter says otherwise. Check the alternator and battery with a Voltmeter. Regardless of the type of charging system, there's always a drop in voltage. So most likely there's no problem with your alternator.

Question: Should a cooling fan connector switch get hot to the touch?

Answer: Not really, unless it's too close to a hot surface, probably the engine or there some unwanted resistance. Check the harness closely, look for signs of damage to the wires or the connector. And make sure it's away from the engine.

Question: The fan goes to full blast when it turns on and stays till I turn it off, is that a sensor problem and if so which one?

Answer: This could be a sensor issue or a stuck relay problem. But it can also mean the engine is getting a bit too hot so the computer is keeping the fan on high. Make sure you don't have an overheating problem. Consult the repair manual for your particular model, there could be a coolant temperature sensor, a separate thermal switch, or a relay issue.

Question: The Engine overheats but the relay is not picking up. What may be the cause?

Answer: Check the temperature switch and relay. Also, make sure they are getting voltage.

Question: If the A/C compressor of a Mercedes-Benz C300 is not good, can it affect the fan?

Answer: Yes. The fan should come on when the AC is working. There could be an issue with the compressor or refrigerant is too low.

Question: I have a 2005 GMC 1500 truck. Cooling fan comes on when the engine is cold, and when I put key in the ignition and turn it to the on position (not start) the fan goes off. I take the key back out and a few minutes later the fan comes back on. The fans don’t come on when the engine is at full temperature either. I changed the block temp sensor and relays and nothing changed. What could be the problem?

Answer: There is a short in the circuit. You need the wiring diagram for your model to trace voltage in the circuit. You can use either a test light or multimeter.

This other post may help:

Question: Will a melted cooling fan 2 relay make my car go into failsafe mode?

Answer: Check the AC compressor. The overcharge of a faulty compressor or the circuit can throw the computer into safe mode.

Question: My engine cuts out when the cooling fan turns on. It is a 1995 Ford Festiva. Why is this?

Answer: The problem could be in the cooling fan circuit, a faulty battery, or (less likely) the charging system. The fan motor could be pulling too much current or the circuit has too much resistance. Have those points checked first.

Question: I have a 2008 Mercedes GL 450. The cooling fan doesn't run even at a high temperature. Turned on the Airconditioner but still doesn't run. What is the problem?

Answer: Check the fan switch (coolant temp sensor) and the circuit. You may need the vehicle repair manual for your model to I.D. the wires.

Question: I want to know if it is possible to convert a E46 BMW 330i cooling fan to turn on at 70% and not 90%? I want the fan to run before it gets to 90 degrees.

Answer: It is possible to do this. The easiest way is to use digital fan controllers. But, then again, the factory switch works in sync with ignition timing, fuel, oil temperature, and many other things to give you better engine performance and minimum emissions. You basically will be reducing engine service life in my opinion.

Question: I have a 2000 Camry 2.2L. The cooling fans come on way too late: only when the temp gauge is very high. They work normally with the AC on. The coolant temperature fan switch/sensor at the bottom of the radiator is new and works as it should in another similar Camry (I switched it out to test). Any Ideas what could be causing this?

Answer: Make sure there’s proper outside air flow through the radiator or condenser (usually bugs clogging passages). Check that the shields around the radiator are in place. Also, a clogging radiator may be preventing proper coolant flow.

Question: Will a blown fuse, (electric cooling fan) stop my 2004 Lincoln Aviator from starting up? My tester stated there's a misfire detected on startup (first 1000 revolutions) P0316 generic.

Answer: This is usually triggered by a problem in the fuel or ignition system. However, double check and make sure there's not another DTC in memory or a pending code. If you find one, check on that area.

Question: So when I get my 2008 GMC Acadia up to temp with AC running and when the cooling fan kicks into high, it blows my 30a fan 1 fuse. When ii started, this fuse issue, both fan 1 30a, and fan 2 40a were blown. Now the 40a hasn't blown, and its currently 80 degrees out. What should I do?

Answer: Check the relays and connectors for the high-speed circuit. There could be a loose wire or the relay may be faulty.

Question: My overheated sensor light does not show when the car is overheated and also does not start cooling fan in Chevrolet Spark 1.0 LS model 2008. However, when A/C using then cooling Fan start and running continuously after the A/C is closed?

Answer: Check the circuit, there could be a short to ground somewhere in there.

Question: I have a 2003 Mercury Marauder. When I turn on the AC on in any setting, it doesn't do anything. I replaced the blower motor still nothing. I was thinking maybe the resistor but then a friend told me that if the radiator fan gets unplugged somehow or just stops working for some reason, that my AC would not work as well. Is this true?

Answer: The AC uses the coolant to dissipate heat. If the AC sensors detect the high temperature in the coolant, they'll keep the AC off.

Question: My engine fan works when the ignition is off. Why is that? Please help?

Answer: On some models, the cooling fan is configured to run after the ignition is removed to remove extra heat from the engine. Since coolant stops circulating and coolant may boil from engine heat, the fan blows air around to engine to help remove this extra heat. The fan may run for several minutes. This is normal.

Question: My radiator fans are not working. They do if they are straight wired. We have replaced the relay and temperature sensor. Can the AC pressure switch cause this? What else could it be?

Answer: Make sure the coolant temperature is reaching operating temperature (thermostat not stuck open); check fuses. The control module is another possibility. There could be another faulty relay or a problem in the wiring harness or connector. You may need to look at the diagram for your particular model to check for other possibly relay or switch in the circuit you are missing. Using a testlight can help you trace voltage in the circuit.

Question: I have a 2006 Mercedes E350. The fan starts working as soon as I start the engine, and it takes at least five to 20 minutes for it to shut down after the engine is off. What could be the issue with my Mercedes engine fan?

Answer: There could be a bad coolant temperature sensor or a stuck AC relay.

Question: The Toyota computer assembly theft warning system is broken in my Toyota Corolla. Is this a huge problem that I should try to fix?

Answer: In some cases, depending on the fault, it may prevent you from starting the engine or cause other issues. If necessary, check with your local dealer if you are using an original system or a reliable independent shop.

Question: I have a Toyota Vitz - KSP90. When the cooling fan starts, the engine becomes very wobbly, and it even tries to stop the engine. After it is turned off, idle speed becomes normal. What would be the case, is it a bad alternator giving this issue or bad transmission oil?

Answer: Have the alternator checked. It might not be responding properly when the load increases. Just to make sure, check the charging circuit voltage drop, to see the condition on the wires and connectors.

Another possibility is a faulty fan motor.

Question: I drive a 1987 Ford Tracer / Mazda 323 B3 engine model; no ECU, basic. The cooling fan was running all the time. Now it doesn't start at all. Replaced a blown 30 amp fuse. Still nothing. If I give the fan a slight push the fan spins. I have noticed the sensor is a bit corroded. Also, the car travels along a very dusty clay road. Could the problem be with the sensor and a dirty fan? How would I go cleaning the fan?

Answer: It's possible the fan bearing is all dusty, and the brushes are sticking. Add some penetrating oil to the bearing and see if it helps. You'll need to work on and test the fan outside the vehicle. Replace the sensor if it is corroded. Sometimes it's necessary to get to the motor to do a more complete job. This video may give you an idea about servicing the fan:

Question: Why is my car's fan not running at high speed when AC is turned on?

Answer: Check the fan relays in the power box in the engine compartment. One of them might not be working properly.

Question: On a 2001 Honda Ex 4 cyl, which side is the condenser?

Answer: I don't have the schematic with me, but if I remember correctly, it's located to the left (driver's side). You can call your local dealer service department to confirm.

Question: I have a 2009 kia Sedona. Neither cooling fan is working and my AC compressor will only engage momentarily right when you start the car. It remains engaged until the time when the cooling fans are meant to come on. Then it disengages and won't reengage until I cycle the ignition. Throwing code p0480. Any advice on where to start?

Answer: There could be a problem with the cooling fan control module. Have it diagnosed first before replacing any components.

Question: The engine is overheating as a cooling fan does not go on. But the fan works when I turn off the engine. Sometimes the fan goes on when I restart the engine after a minute, and there is no more overheating for the next drive. But in that case, I think the fan works longer (sometimes nonstop). What could be the problem?

Answer: These type of intermittent faults are sometimes hard to diagnose. But they usually come from a faulty wire, connection or sensor. It's possible a loose wire or faulty sensor is not sending the correct signal to the computer when it should, then grounding the circuit to make the cooling fan operate. Check for diagnostic trouble codes, even if the check engine light is not on. Then inspect the wires and connectors to the cooling fan closely. You may need the diagram for your particular model to check the circuit. You can use a test light or digital multimeter for this.

© 2017 Dan Ferrell


Dan Ferrell (author) on August 19, 2020:

So your condenser fan isn't working. Turn on the AC and set it to MAX when at idle and see if it comes on. Follow the steps in the "Troubleshooting Your Cooling Fan" section. Depending on your results, you may need the diagram for your particular model to check the fan motor and circuit. Hope this helps.

Chevygirl68 on August 18, 2020:

Hi, I have a 2000 Toyota Celica GT. It has two fans, the Radiator fan seams fine. The fan on the drivers side , under the air cleaner is not running. It's not frozen it moves freely. The inside fuse is good, now what ? Please hepl.

Dan Ferrell (author) on August 04, 2020:

If the connector melted again, make sure it's not touching a hot engine surface or components (e.g. exhaust manifold); otherwise, there could be a circuit problem causing that part of the circuit to get hot. Hope this helps.

Jenger on August 02, 2020:

Replaced radiator fan assembly on 2014 Nissan Pathfinder because of melted connector plug connecting module to car. Same thing happened to the new one. What would cause this? Please respond. Thank you!

Dan Ferrell (author) on June 25, 2020:

First make sure you got good spark and fuel pressure. If you do, then there could be a problem with a sensor. Download trouble codes, even if the engine light is not on. There could be a pending code. Hope this helps.

Andy on June 24, 2020:

My nissan almera swing the engen bt doesn't run out. What may be the problem? Seems like fuel pump is working.

Dan Ferrell (author) on November 02, 2019:

Have the alternator checked. It might not responding properly when the load increases. Just to make sure, check the charging circuit voltage drop, to see the condition on the wires and connectors.

Other possibility is a faulty fan motor. Hope this helps.

Rwhr on November 02, 2019:

I have a vitz ksp90 model. Every time cooling fan starts engine getting wobbly. After it turned off its become okay.

Dan Ferrell (author) on October 26, 2019:

Check the cooling fan temperature switch or sensor. It might be stuck.

Mekonnen Seid on October 26, 2019:

Hi Sir. Currently I purchased used toyota vitz 2001 model car. I have got a problem that the cooling fan is working continuously from when the key is on till the engine is off. I think it works abnormally. Sir what is the cause od this problem? Should I stop the car or can drive with tilhis problem. Pls. Help#

Dan Ferrell (author) on October 07, 2019:

There might be too much resistance in the circuit. Look for loos or corroded wires-connectors. If necessary, check the engine grounds.

Sean on October 07, 2019:

When my AC is on, my corolla fan is always spin low till the engine gets hot..

During idle the fan always take long before it comes up.

Amyia Adans on October 03, 2019:

My son will come on but it'll run slow and stop.

Dan Ferrell (author) on July 29, 2019:

If fan motors are working, and voltage is present at the plug, then the problem could be in the circuit. Check the relays, temp switch.

GearheadRA168E on July 29, 2019:

2002 acura rsx auto (overheating)radiator cracked while driving replaced with a new one and switched everything from old to new radiator components but took off the a/c condenser and now, car starts good idle for about 10min and starts overheat fans dont come on, i checked fans motors itself work and fan plugs receiving voltage also checked fuses, wiring harness, havent checked the relays, fan or temp switches,thermostat..before the radiator cracked everything worked good


Dan Ferrell (author) on July 27, 2019:

Make sure the fan belt (if equipped) is not loose; check the belt that runs the water pump; listen to the water pump with a mechanic's stethoscope or a length of hose. If it is noisy, the bearing or impeller may be faulty. Check that the cooling fan is coming on when the engine reaches operating temperature. Also, make sure your coolant is still good and the system has enough coolant. Hope this helps.

Todd on July 27, 2019:

Car runs hot idling but is fine while moving

Dan Ferrell (author) on July 26, 2019:

Make sure the engine is not overheating, causing the fan to come on. If not overheating, check for a faulty coolant temperature sensor.

joel on July 25, 2019:

why does my radiator fan turn on when it want to? How do i fix that...

Dan Ferrell (author) on July 09, 2019:

I'm glad it helped. Thanks.

Anonymous on July 09, 2019:

Hi, just wanted to say a big thanks! We were having some trouble with our car overheating on a road trip, and we had turned the A/C off along with anything else that we didn't need to have running, but it turned out that the fans weren't spinning when the car was overheating, so I guess it was a bad temperature sensor or circuit, but we turned the A/C on and were able to finish our road trip, so thanks!

Dan Ferrell (author) on July 06, 2019:

Check the manual for your particular model. The AC has a feed line to command, depending on configuration, the fan on (condenser or cooling fan). Low speed after AC is turned off most likely comes from AC.

Robert1958 on July 06, 2019:

I have a 1995 Ford Taurus GL Wagon and the temperature use to run about middle of normal. Recently it rose to the L in normal and I had flushed the system, changed both temperature sensors. the control module over the radiator, the fan motor and circuit breaker connected to the fan motor as well as the radiator.


I just checked the water pump with a long screwdriver and my ear to it, no noisy bearing sound, just low pitch steady hum, no leaks out leep hole. Coolant is flowing steady through radiator, [about the A in normal], just before fan comes on, coolant starts to rise through open neck,[ about the end of L in normal], of radiator then goes down into radiator again and flows through radiator no problem, [A in normal again] when fan is on. Put the A/C on after fan is off off and the fan goes on high, then I noticed when I shut A/C down, the fan is on a low speed for a little bit then goes off. I do not notice a low speed fan when my A/C is off, just a high speed fan when the gauge reads the end of L in normal.

Dan Ferrell (author) on July 04, 2019:

If the thermostat is old, you may want to replace it as well. You can listen to the water pump with a length of hose and see if the bearing or noises come from it. The impeller may be loose. Check the belt that runs the pump. That can also be a problem. Although not that common, the temperature gauge may also become faulty. Hope this helps.

Robert1958 on July 04, 2019:

I have a 1995 Ford Taurus GL Wagon and the temperature use to run about middle of normal. Recently it rose to the L in normal and I had flushed the system, changed both temperature sensors. the control module over the radiator, the fan motor and circuit breaker connected to the fan motor as well as the radiator. Only thing not replaced I know of is water pump. Still runs hot, between L and Hot on highway, fan is coming on about the L. Comes on when A/C is on. Can the water pump cause this? Only thing I have not replaced I think. Any Suggestions?

Dan Ferrell (author) on June 27, 2019:

Probably the fan bearing is getting dry or worn. When you spin the fan manually, your help the bearing overcome whatever gets it to stick. Probably you need a new fan motor.

Malik Khalid on June 27, 2019:

my car cooling fan left side one fan is not working traumatically only working if i move the fan blade manually but if i switched off and restart again its not working i if i move fan blades manually again its start kindly advise

Dan Ferrell (author) on May 20, 2019:

Check the condenser for clogging (bugs, debris). It is located near the radiator and looks like a small radiator. Also, check that the system is still charged. Otherwise, check the compressor.

Emma on May 18, 2019:

My 2007 Camry doesn't blow cold, but it blows hot when I turn the dial to heat, What could be the problem?

Dan Ferrell (author) on May 08, 2019:

You may want to take a temperature reading of the engine block and inlet radiator tank once the fans come on. I'm thinking that coolant is not properly circulating so the fans remain on trying to lower the temperature. Another possibility is a failing temperature sensor. A normal engine operating range is between 195 and 220F.

GJA on May 07, 2019:

Hyundai 2006 Elantra radiator fans come on once car is warmed up and stay on until engine is off

I'm trying to troubleshoot and also wondering can I just ignore this if there are no other problems. How much wear and tear is really going on if the fans stay on during driving? I've read that fans generally don't fail, but this seems like a lot of unnecessary spinning.

I only noticed this because I did some maintenance on my coolant system. Not sure when the fan issue started. No overheating indicated on the temp gauge currently. There are no symptoms I'm noticing otherwise.

I know that in the past the fans use to cycle on for 10-15 seconds and then go off while idling. Now they just stay on after the car is warmed up and don't go off until the engine is turned off.

Climate control is off when I've tested the fans. A/C will turn on the fans immediately with engine cold and keep them on.

Fuses are in tact. Not sure if relays could still be an issue. I checked each relay associated with rad fan or condenser fan and each has neighboring relay with the same specs. I swapped each corresponding one and fired up the car, no changes.

Unclear if the ECT (coolant temp sensor) is malfunctioning. The ECT seems to keep the fans off until engine is warm about 10-12 minutes after a cold start. If I disconnect the ECT for a moment while the engine is still cold the fans go on. The fans also continue if I disconnecting the ECT while the engine is hot. So the ECT is doing some work it seems, but is it possible it or maybe something else is keeping the fans on?

Dan Ferrell (author) on April 27, 2019:

You can check the wiring diagram for your particular model. Get an aftermarket manual to trace the circuit. If you don't have the manual or don't want to buy one yet, check, the reference section of your public library, probably the have the manual.

Dan Ferrell (author) on April 27, 2019:

The computer monitors the signals from the sensor. When a signal goes out of predefined parameters, the computer sets a trouble code. Look for the definition of the code online and you'll get an idea about the problem.

Christine C Atherton on April 26, 2019:

I got a thermostat sensor code on the OBD my question is could a relay cause the thermostat sensor code

G.Balaji on April 25, 2019:

J 293 coolant fan control module p1672fan 1control circuit open circuit / short circuit to ground

Dan Ferrell (author) on December 31, 2018:

Not yet. At least. The fan problem may be related to the expansion valve and the overall operation of the AC. If you're going ahead and replace the compressor, go ahead. And talk to your mechanic about the fan operation. But I'd suggest to wait until you got the AC system up and running good. Hope this helps.

Roody on December 30, 2018:

Hi, I have an 05 Dodge Magnum, I was trying to change the expansion valve myself and one of the bolt was broken and I was replaced it with just one bolt because I did not know if the bolt was mounted on a seal plate I thought I would have to remove the evaporator another for me to remove the bolt, I said I'm going to leave it with one bolt, I was scared to tell the A/C guy was going to vacuum and fill the A/C system for me. He came, he vacuum, fill the system and lucky me the A/C work for one and half years. After that I started to smell the Freon inside of the car and the A/C started to blowing hot air. I called the A/C guy again and told him to come check the A/C for me, before that I went ahead and put some A/C stop leak which worked for thee days, now I went to the A/C guy and I told him what I did before I went to him. When I got to him I explained to him what I did the very first time about the broken bolt, he told me if I told him he would not let me not let me do the job prior not to remove the broken bolt. He told me he got a good A/C stop leak could put that will fix it definitely but before he ad it into the system it is a must and imperative to remove the broken bolt first the Expansion Valve. Before he did the he ad some freon he told me he want to see how long it going to stay before the A/C the get hot again which he did, and it took it ten days the A/C got hot. I bought this Expansion Valve kit he replaced, vacuumed and filled the system but he told me as he replaced the part that was for him the main cause of the leak, he is not going to ad the A/C stop leak yet. He vacuumed/filled the system and he told me this time if the A/C got hot that's when he will have to ad the A/C stop leak. This time it was running a little longer for about three weeks. All these happened because I don't want to replace the evaporator. He always telling me that the A/C compressor is very weak because when the car is idling the A/C dosen't work good. Now my concern is the cooling fans, they works but it like they don't work at high speed like they used to. I don't know if it is because it's spring time it's not too hot. I had even turned the heater on, the fans just work normal. I did an experience, i unplugged the fans I accelerated the car and the temperature went up and I went and plugged the fans back and they kicked on in very high speed just once, after that they're running at low speed. Do you think the fans need to be replaced or not.

Dan Ferrell (author) on December 27, 2018:

The usually won’t come on until the engine is at operating temperature (around 190 o 210 degrees). Than it will run at low speed (mostly) or high speed to maintain coolant temperature. You can check the specs for your particular model using your vehicle repair manual. If you suspect something is not right you may want to check the engine coolant sensor or switch.

sizar on December 26, 2018:

the cooling fan won't come on at 96° ...

it start at low speed at 105° ...

why ?

Dan Ferrell (author) on September 27, 2018:

Check for power to the relay with the ignition On first. Other possibilities is a defective or disconnected module. If there's no problem with the AC, you may use the diagram to trace for voltage. You can find the diagram in the repair manual for your vehicle. Use an aftermarket manual, if necessary.

Dan Ferrell (author) on September 27, 2018:

Check the temperature sensor. If the sensor is fine, check the wires. Make sure they are well connected, not loose.

Kayla54701 on September 27, 2018:

I have a 2006 Dodge caravan, I had the radiator replaced about 6 months ago my recent problem is the fan comes on when it's not even warmed up, once it comes on it seems to stay on until I turn my van off.

Chinedu on September 27, 2018:

My Hyjndai Azera 2009 fan wont start, fan tested okay, relay tested okay, module tested okay. There seems to be no power to the relay and module. Been battling for 3days now

Dan Ferrell (author) on September 21, 2018:

Hi RR,

It's possible. If you think the fan is running when it shouldn't check for possible DTCs, even if your engine light is not on. You may need your repair manual to check on some sensors.

Rick Brooks on September 21, 2018:

On 2009 GMC with 5.3 L . Can the ambient temperature sensor cause electric radiator fan to run even when engine is overnight cold when AC is on for several minutes as I drive ?

Dan Ferrell (author) on September 10, 2018:


Follow the voltage using a diagram. Both fans should come on at the same time - they're wired in parallel. Check where the voltage is stuck for that side.

Sorry can't be of any more help.

R Harris on September 10, 2018:

I have a 2006 Pontiac Grand Prix 3.8 Supercharged. I have replaced: Coolant temperature sensor, thermostat, PCM, Both fans (complete unit), Wiring from the fans to the relays and plugs oh and the relays yet the driver side fan still wont come on. Fans have been tested both the old and new (and they worked), but I can't get this fixed. Any suggestions?

Dan Ferrell (author) on September 07, 2018:

Yes. If the engine starts to overheat, you can end up with an expensive repair. So it's better to take a look at it now that can be much cheaper.

shannon dillon on September 06, 2018:

it is a good idea to get someone to check it out if you have a problem with the fan cooling system

Dan Ferrell (author) on August 29, 2018:

It's possible there's a failing pressure switch in the AC. If you have a capable scanner, the circuit may be monitor to check the switches.

Hamid on August 29, 2018:

Hi, I have Mitsubishi gallant v6 2004. My cooling fans does come on and with AC on they do increases speed but not to the max speed even when the engine is overheating. They stay on same speed without AC even if the needle is going above the middle. Only increases speed with AC on, but not very fast just little difference. If I unplugged the ECU wire from the module main connector they run full speed all the time and no heating issue.

Dan Ferrell (author) on June 01, 2018:

Hi RW,

Sorry, I don't have the wiring diagram for this model but look for the fuse box, either under the dashboard or in the engine bay, ---firewall, driver's side possibly.

Hope this helps

Ray Waldin-Walker on June 01, 2018:

I have a 1992 Volkswagen Hatchback 1Lt petrol, "the old bread van", boils when reaches over temp, ok when air cools eng on a run till i stop. fan motor ok, checked with 12v source separate, changed rad sensor, no go where is rad motor relay?

Dan Ferrell (author) on April 10, 2018:

Hi Prasit,

You need the wiring diagram for the cooling fan of your particular vehicle make and model. Recheck the connections you made and the fuses. It seems that somewhere you created a short. If you replaced the cooling fan, make sure it's the right one for your model. If you don't have the manual for your car, check the reference section of your local public library.

Good luck

Prasit on April 10, 2018:

My Toyota Soluna 1997 5A-FE 2 ECM's Resistor, Diode and transistor burnt out , after replaced plug into Car Cooling Fan running immediately and Magnetic Clutch of AIR Cond not be operated then ECM burnt in same position excluded Diode (Engine can be start and running)

Would you please diagnoses the major shorts.

Thank you

Dan Ferrell (author) on April 07, 2018:

Hi Mike,

Basically the black wire is ground and the blue one is positive. I don't have the wiring diagram for your model, but I'm assuming you are connecting to the control module. Check the fuse and make sure there's power. If you don't have the service manual for your particular model, stop by your local public library. The reference section might have the manual for your model.

Good luck.

MikeN70 on April 07, 2018:

I recently purchased a new Universal 120w cooling fan for my BMW 318iS. The wires from the car are brown, blue, another colour with a stripe in. The universal fan has only 2 wires, one black & one blue. Which wires need to be connected to allow the fan come on when the car gets hot.

Presently the striped wire is not connected & after driving about 12 kilometers the temp gauge started to rise & the fan did not come on.

Please help!

Dan Ferrell (author) on March 19, 2018:

Hi murlly

It's possibly there's a short circuit or a problem in the cooling system. Try scanning for trouble codes, if necessary.

Good luck

murlly on March 18, 2018:

Tkz for good information car problem model chevrolet nabira 1.8 sport cooling fan sometimes non stop run 30 minit sumting and aircond automaticly cut off.. after 30 minit normal running cooling function

Dan Ferrell (author) on November 11, 2017:

Glad it helped.

Thanks for the comment.

Good luck

Adam O. on November 11, 2017:

Man, this helped out a lot!! Well written / explained! Thank u.

Related Articles