Oldsmobile/Buick Repair: 1990 Oldsmobile ninety eight a/c blows from front vents sometimes, oldsmobile ninety eight, switch modes

Question
my a/c works really well, but most of the time it wont blow from the front vents. All the rest work fine,  sometimes I can hear like something opening or closing then it will work fine, if I leave the a/c on when I turn the key off sometimes it still flows out of the front vents, but most the time again it wont come out of the front vents.  Every now and then if you hit a bumb the a/c will start flowing throught the front vents but not often.

Answer
Hi Eva,
Sounds like a door sticking, and hard to say what might fix it.
If the door is vacuum controlled, a leak anywhere in the vacuum supply system could cause it to not quite have enough to move it till the bump.
If that is the case, I would expect it to seem like it has a mind of its own, and switch modes as you start up a hill, or start down one after going up, like an overpass.

Van