Skip to main content

Troubleshooting Electric Cooling Fan Problems in Cars

Dan Ferrell writes about DIY car maintenance and repair. He has certifications in Automation and Control Technology and Technical Writing.

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 a 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.

Scroll to Continue

Read More from AxleAddict

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, in 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 at around 200°F (93°C) or less, the temperature switch or sensor may fail to trigger the radiator fan.

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.

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 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

Related Articles