1997 mercury tracer overheat fan not turning on?

1997 mercury tracer same as ford escort 69k miles started to overheat because my radiator fan won't turn on i've change the engine temperature sensor didn't help. But when ac is on fan does turn on and car doesn't overheat with ac.

There may be more then one temperature sensor. One is for the temp gauge and the other one is for the PCM.
Make sure all the air is out of the cooling system by running the motor for 15 minutes with the radiator cap off.
Replacing the thermostat is always a good idea when the motor tends to overheat.
The radiator fan should come on when the coolant gets to 225 degrees.

Check the radiator fan relay. Heck the radiator fan fuse. See if you can run the fan jumping it with 12 volts