Is your fan coming on???

The AC should have little bearing on it, as it uses it's own "radiator". It does have some bearing as it uses power from the engine to run the pump, but not much more than an alternator.

I would suggest seeing if your cooling fan(the one for the radiator) is coming on or not. If it's not, you may need a new thermo-switch. This is the switch that tells the ECU how hot the engine is and when to turn the fan on. Most of the time they are located in the thermostat housing. Someone may be able to direct you better than I can though.