I think, without actually going out in the car to confirm, that anytime you push the AC button it turns the compressor off except when in the window defrost mode - then the AC runs all the time. Also the dual mode doesn't work when in the window defrost mode - only the temperature for the drivers dial lights up.

Edit - You're correct - I just checked it out and if you push recirculate the AC comes on. I guess the engineers don't want you to fog up.