I remember a long time ago running across a mod that let the driver control when the AC compressor turned on, a.k.a. you put a switch in to kill the power to the compressor when you were using defrost, anyone have a link?
I feel thats not a very good idea at all! (1) mentioned above your defrost will not work as well as it should.(2) without your compressor" pump" never spinning things are going to start drying up,[ie] the vanes in the pump,o-rings,ect. If you're looking to improve fuel consumption look in to removing the mechanical fan with another electric....a popular/cheap swap is the from a Ford Taurus. Just a suggestion