Electric Cooling Fan – What can stop it from working properly and why.

Electric Cooling Fan - What Can Stop It From Working Properly And Why
Electric Cooling Fan - What Can Stop It From Working Properly And Why

If your engine is overheating, or shows signs of running hotter than normal; you may have a problem with your electric cooling fan.

Electric cooling fans are used, to move air through the radiator; when the vehicle is not in motion.

Consequently, any problem with the electric cooling fan can stop it from, transferring heat away from the radiator.

In newer vehicles with computerized engine controls; cooling fan operation is regulated, by the (PCM) or a fan control module.

So, input from the engine coolant sensor, ambient air temperature, vehicle speed sensor and other sensors; are sent to the (PCM). As a result, the (PCM) uses this information to decide; when the electric cooling fan needs to be energized.

The electric cooling fan saves energy by only running, when it needs to remove excess heat away from the engine. Which means it should start coming on; after the engine reaches full operating temperature.

Electric Cooling Fan - What Can Stop It From Working Properly And Why
Electric Cooling Fan – What Can Stop It From Working Properly And Why

Consequently, if your electric cooling fan isn’t coming on; you can bet there’s something wrong with the fan assembly, the circuit, or one of its components. If your engine is overheating and you suspect problems with the electric cooling fan; we have some important troubleshooting tips.

Fan Function

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.

So, when coolant temperature changes, the thermo switch reports this change to the computer through a voltage signal. Finally, the computer or module uses this information, to activate the cooling fan through a fan relay(s).

What Can Stop Your Fan From Working:

  • Defective temperature switch, (ECT) sensor or other sensor
  • Engine thermostat is stuck OPEN (engine never gets hot enough to turn on the fan)
  • Faulty fan relay
  • A wiring problem (blown fuse, loose or corroded connector, shorts, opens, etc.)
  • Bad fan motor
  • Defective fan control module

How To Test Your Engine Cooling Fan Motor

The Quick Test

So, one quick way to check the fan is to start the engine and turn on the A/C to max. If the fan runs, the fan motor, relay, fuse and wiring are all okay.

Test the fan by connecting it directly to battery power

The fan motor itself can be checked by using jumper wires. Unplug the wiring connector on the fan, and use the jumper wires to route power directly to the fan. If the fan motor is good, the fan should spin at normal speed when supplied with 12 volts.

Check for any blown fuses or a tripping breaker
Check for any blown fuses or a tripping breaker

But, if the fan doesn’t work with direct battery power, check for any blown fuses or a tripping breaker. If you find a blown fuse or tripped breaker, the fan motor might be pulling too much voltage. Check for a shorted wire or replace the fan motor.

Testing The Engine Cooling Fan Temperature Switch

You can test the cooling fan temperature switch, using a test light:

  • Connect your test light to battery ground.
  • Start and idle the engine, and back probe the connector terminals with the test light. One of them should turn on the test light.
  • Wait for the engine to reach operating temperature.
  • Now back probe the other wire at the connector. Your test light should come on. Otherwise, the switch is not working.

Testing The Cooling Fan Relay

The relay is a critical part of a cooling system. When it malfunctions or breaks down, it affects the fan. The problem spreads to the rest of the cooling system, the engine, and the entire vehicle.

The easiest way to know whether your relay is causing trouble is to replace it with another relay. Check the power center for a similar relay. Something 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 Fuel Pump Relay – Function And Testing Procedures. The steps are the same for your relay.

Replace it with another relay.
Replace it with another relay.

Still another DIY test involves shaking the cooling fan relay and listening for any noises. Consequently, a broken armature will rattle around the relay.


So, when checking for engine cooling fan problems, a modern vehicle may present a challenge. Consequently, some fan circuits are wired so the fan can come on at any time. Whether the engine is running or not. Finally, keep fingers and tools away from the fan blades.

Thank You !