Volvo Repair: a/c, vacuum switch, vacuum system

Question
The a/c vents out the defroster vents only. Regardless what vent you put it on it only vents out the defroster vent. I went to the junkyard and bought a new positioner - the only way I can describe it - the thing that moves it from one port to the other. Didn't help.
Help! What do I do next? 1985 Volvo 740GLE
Thanks,
Fred

Answer
Hi Fred,

      Did you check out the vacuum system...it operates ALL the various vent doors..any kind of hissing is n/g.
        You should be able to find the master vacuum feed and
   feed vacuum to the various ports...and feel different  doors open...my 85 gle had a problem in that area too.
I remember mine leaked if the switch was moved in a certain way.
  
    The vacuum switch you got from the junk yard...maybe n/g.

         Bye,

            Bilbo