Ok, 87 gt, auto, 222,800 miles, something is bound to go wrong.

Ok my problem is that the radiator cooling fan only comes on if I press the AC MAX button.

No other time.

I changed the coolant temp sensor, the fan relay, many things...

What did I miss, and what can cause this?

If you changed the CTS that is the wrong one. There is actually a Radiator fan switch.
If you ground the wire to the swich and the ran runs (key on of course) then you know the wiring is good and the swich has failed. (or unlikely lost it's ground through the manifold)

[This message has been edited by Dodgerunner (edited 12-02-2012).]

Changed that too, that's the single wire sensor on the topside of the engine. That was done.

Did you test the wire by grounding it? If you did and it did not run then you have a wiring or connector problem somewhere between the engine and the AC control head since the control is all on the same wire.
What did you use to seal the new switch?

[This message has been edited by Dodgerunner (edited 12-02-2012).]

Are you sure the car is getting hot enough?

The factory switch only activates around 235 F.

quote Originally posted by masospaghetti: Are you sure the car is getting hot enough? The factory switch only activates around 235 F.

This. It's a bit past mid-guage on my car, and always feels like the car is going to over heat before those fans kick on, lol.

quote Originally posted by One wicked svt:, and what can cause this?

The weather pack on the male end, if it's hot try playing with it using needlenose pliers, if the fan kicks on when you press it down, then it's the weather terminal, push it down, I gave up on those a long time ago, I removed them completely, I just removed the male end pack, put a new male pin on the end of the wire, on both my V6 cars.