Defroster to floor to vents adjustment

Has anyone else had the following problem with their Cavalier?

The problem is that there is no difference when I turn the adjustment knob for the fan, the speed control works but to change from Vent to Bi Lev to floor to blend to Defrost the air continues to blow equally between the windshield vent/ front vents and floor. The only thing that does happen is that in recirc or Defrost it does engage the AC compressor.

I am able to keep the windshield clear defrost/defoging by closing the four front vents and turning the speed to full blast.

Since I am able to get by I have not wanted to take it to the shop and pay $$$ / hour just to diagnose and than additional to fix.

I am hoping some one else has had this experience and then I can give direction to a probable cause if I take it in.

Oh and I forgot to mention it just stopped working one day, I had never until 2 weeks ago removed any dash components at all.

If it matters, 1999 Z24

Thanks in advance

usually there is a vacumm line that gets broke> i think it is either what or gray. Try a look see and check for breaks in the. If it is something simple like it just broke in one part then it's an ez fix