77 ac problem help please

[77 MB 300D lady]

I have a 1977 300D that has ac issues. I recently had a new compressor put in (which a chrysler is the only thing that fit it) someone that owned it prior to me really messed up the wireing and put some type of by-pass stuff of it. Plus they cut some of the vaccum lines and really messsed this up too. One mechanic that deals with the older models said to wire ac straight to the battery.... well it drains my battery and the alternator, now what???? Anyone have any suggestions or a wireing diagram and vaccum scamatic for my ole' girl? Thanks Susan