Chevrolet Engine cooling fan not running

Cooling fan not running on Chevy cavalier

The engine cooling fan not working causing engine to run hot, but fan does operate when defrost or a/c are used.

So i don't think fan is actually the issue.




UNDERSTANDING OF THE PROBLEM:----
The fan turns on when A/c or heater is turned ON, the engine temperature will sit where it is supposed to.
  I.E. it does not run hot as long as the fan is on.

 but if the A/c is not turned ON then fan will not come ON and engine overheats.

See below the wiring diagram for cooling fan:-----

The fan turns on via air conditioning or via coolant temperature.

So its coming on with A/c and heater turned on,but not coming on when the coolant temperature gives the command.


The fan is controlled by same relay and same fuse to turn on,whether its by A/c or coolant temperature.

And now when we know that fan is running when command is from A/c so its clear that fuse and relays are working fine.

Both the ac position and the coolant temperature sensor sends signal to ECM(Computer) to turn on the fan, then the engine computer sends that signal to the relay


So now its confirmed that relay or fuse is extremely unlikely to be the issue

The problem is most probably the coolant temperature sensor, the alternative would be a faulty engine control module or faulty wiring between the coolant temperature sensor and the engine control module.

If you notice CHECK ENGINE LIGHT COMING UP ON DASH,then most likely its faulty coolant sensor.But if No check engine light then issue will be mostly the faulty ECM( Computer module).

See below the coolant sensor location diagram for your Chevy model:----

These details will help.
Thanks.