A/C problems
 

I drive a 97 ranger 3.0 v6. My air only blows out of the defroster no matter what setting.I have good vacuum pull untill i get to the harness that connects to the switch ive replaced both the switch and the hose harness with new parts and the same problem has happend, a hissing between the hose harness and the switch,ive gone to junkyards replaced the two and have had the same problem.Is there any information i could be overlooking?Any hepl would be appreciated.