Vacuum leak

Over the summer I had the heater box rebuilt professionally and I replaced the a/c & heater switch on my 71 Scamp. Actually the whole car is being redone and rewired. Anyway I have no vacuum which I'm looking for the leak now. My question is do I need vacuum for the switch to energize the a/c system. When switched to a/c I have no power going out to the compressor. And no there is no a/c system yet under the hood. I'm still in trouble shooting mode, just trying to figure some stuff out.