A broken cooling fan can cause your engine to overheat and even cause damage to the water pump. Learn how to troubleshoot an electric fan that refuses to work. If you have a basic knowledge of electricity and electrical circuits, this will be an easy task. In a matter of minutes, you will be able to determine the cause and--in most cases--repair that broken cooler fan yourself.
Things You'll Need
- Voltage test light
- Two spare wires 2 to 3 feet long
Check for broken wires or loose connectors around the fan circuit. Inspect connectors at the fan motor, relay, sensor or heat sensitive switch, and the Electronic Control Module (ECM)--your car’s computer control system. Also, make sure to check for a possible blown fan fuse. These are common and overlooked troublesome spots that may cause a fan to fail.
Run and bring the engine to warm temperature. With the engine running, use a voltage test light to check for power to the motor fan. Be extra careful and make sure to keep your hands and tools away from the belt, fan or any other engine moving parts. If voltage is reaching the fan motor, the test light should glow.
Turn off the engine after you see the light glow. Apply direct voltage to the fan motor from your car battery using a pair of spare wires. If the fan fails to operate, replace the fan motor. If the motor operates, your problem is in the motor connector.
Locate the heat-sensitive switch or heating sensor if the fan motor operates with direct voltage and the test light did not glow. You should find the sensor in the radiator, engine block, or thermostat housing.
Measure the resistance across the heating sensor with the multimeter. With the engine at cool temperature (engine off), it should register infinite resistance; with the engine at warm temperature (engine off), you should read low resistance. If both readings state infinite resistance install a new heating sensor, that’s the cause of your failing fan.
Check the action of the fan relay if the heating sensor is registering variable resistance. Your service manual should specify the power and ground wires according to color codes and the proper way to test it. If the fan relay fails the test replace it with a new one.
Check the connections going to the ECM after you determine the fan relay is working properly. If you find broken wires or loose connectors, make the necessary repairs. If you suspect a defective ECM take your vehicle to a service shop for a computer analysis. In most cases, the ECM is rare to be the cause of a failing fan. The above steps should take you to the root cause of your problem and help you fix the cooler fan.
Tips & Warnings
- Most automotive service manuals will show the wiring diagrams for the different electrical and electronic system components. Having the service manual for your car handy to locate components and look up specifications will make your troubleshooting task much easier.
- A service manual can be purchased at most auto part stores. Also, most public libraries maintain an updated section of automotive service manuals that you can consult free of charge.
- Keep your hands away from the fan, belts, or any other moving parts while working on your engine, they can easily catch and rip through your fingers, hands and arms.
- Always wear short sleeve shirts and avoid wearing jewelry or watches while working on your car engine, especially while the engine is running. Clothes and jewelry can get trapped in moving engine parts and cause severe injury.
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