that line under the hood runs to a box behind the dash then to the vac pumps that move the vent controls levers. so you may hear a hiss under the dash if one of the inside car line broke, or the vac pump its self.
ive seen on the board here where the unit does go bad, then others who changed it and still didnt get it to work.
these levers are plastic under the dash, they break all by themselves sometimes. so if you open up the dash some you can see if the vac pumps are moving, if they are the lever arms snapped.
this how to is for the blend door actuators, but the vac pumps are right there next to them, its the round part in the lower right of the first pic. theres one on the pass side as well, removing the glove box door gives you full view of that side.
http://www.grandprixforums.net/showt...door+actuators
