A/C causes condensation on wind screen

Greetings citizens, my trusty 82 380SEC is not without it's idiosyncrasies. That said, and after reading every relavant thread I still am no closer to understanding how it doe's that. I have only 60*F at the vent and so much condensate collecting on the exterior of the windscreen that I need the wipers to clear. Is there a flap thats open or closed that should be the other way? All the biggy parts have been replaced, ie, compressor, dryer, expansion valve, climate control module,a/c muffler/hose assembly. Any input on this problem will be greatly appreaciated. Thanx to all, Luigi.