there are servos behind the dash with diaphrams that go out. Take to a shop that knows how to diagnose the a/c systems and pay to have them go thru it. I had the same problem on mine and it was worth it to have Euro Motors in Santa Monica, CA go thru it and repair it in an hour and a half. In fact, i got the referral to him from this site. now i have air coming thru the vents just fine, now just have to replace the compresser/dryer and make the conversion to R134A

Good luck.

Torie