A/C and heat will only blow out of defrost vents. How can I fix this problem? on 1995 Cadillac DeVille

Most of the time the A/C air comes out of the defrost, but sparatically it will come out of the regular vents for a short period of time and then it goes back to the defrost vents. The heat always comes out of the defrost vents. I have tried checking for vacume leaks and didnt find any that was obvious.

Asked by for the 1995 Cadillac DeVille
1 answer
sounds like an accuator door is binding...Try to operate it by hand...The diaphram inside a module that operates the door may be leaking vacuum.