Heater fan won't change positions

[chevguy]

Hi everyone, I have a question. My wife has a 94 Cavalier, and the other day it started blowing out of only the dash vents. You can't change it to your feet, or worse yet, defrost. My Mom's Corsica had a similar problem and it turned out that it was one of the vacuum lines had fallen off of the back of the switch. So I pulled apart the heater controls on the Cav., but everything seemed to be attached alright. The only strange thing I noticed was that the pink vacuum line had a small amount of suction on it, while the others had none. (This may in fact be the way it's supposed to be, I'm just not sure.) Any ideas as to what could be wrong, and/or how to fix it?

Thanks
Evan