72 demon A/C electrical help

Yes it sounds like part of the harness is missing; there should be a 2 pin connector to the 5 position electrical/vacuum switch for the blower AND a 2nd piggyback switch on the back of that switch assy for the compressor with a couple more wires. Not sure if this is totally separate from the main harness or not.

Look at the left hand side of page 290 in the Classic Industires Mopar catalog to see what the correct switch looks like.