Contour Enthusiasts Group Archives Forums General Troubleshooting Engine runs hot with A/C on

Max a/c position should have no effect since all it does is shut off outside air intake.
My cars usually run at least a full letter on the gauge higher with a/c on in 90 F temperatures at highway speed limits.
You could always get an a/c shop to test it to see if it needs a top-up of refrigerant, particularly if you have never had it checked it since new.