"HOT" running 2.3

[BigEd]

My son's 87 LX 2.3 has a problem with the radiator fan. It won't come on before the temp gauge show that it's already in the red zone. That's too hot for me. I have replaced the fan temperature switch twice and checked the first replacement with an ohmeter and a torch and it does work. I have checked the fan circuit by grounding the fan switch wire and the fan runs. Questions:
1) Where does the fan switch supposed to screw in (it is screwed in to the bottom of the intake on my son's car)
2) What setpoint is that switch supposed to be, can I get one of a lower range and how.
3) Any one else heard of this problem.

Remember, I have checked the whole fan circuit to be OK by turning on the AC and by grounding the fan temp sensing wire.

Any help appreciated