rad fan problem

I have a 2000 sunfire 2.2l auto tran 48000 km. The problem is the fan won't come on when temp goes above 90 C . The fan does come on when the A/C
is turn on so yes fan works. Checked fan relay seems to work and temp sensor has correct ohm readings. After I checked relay and temp sensor It did come on once, but later it didn't work again. If temp gets to high I turn on A/C then temp comes down.

Thanks

what do you call too high of temp? mine will run up to 3/4 mark before it cuts in

The fan used to come on when it went past 90 C or 194 F now
it doesn't.

The fan used to come on when it went past 90 C or 194 F now
it doesn't. But does it come on when it reaches the 3/4 mark It should not have to come on when it reaches just past 90 c. when selector is set to defrost it may come on I know a/c will cycle then in defrost mode