Compressor runs when the defrost is on, hot or cold air. It helps remove the moisture from the air blowing on the glass.
I guess you could install a switch inline to the compressor, but then you'd need to remember to turn it on...
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.