03 Taurus AC?

I noticed that when I switch my climate control to anything but off, my AC pump engages. This affects my gas milage negatively. Can I have a professional install a switch so I can manually byp the pump except when I need it for AC or Defrost? Is there any reason why I should not do this? I'd like to be able to run the heater and/or vent to push air without the pump being on.