GMC Repair: 1999 GMC Safari A/C, side kick panel, vacuum problem

Question
The air only comes out of my defroster and passenger floor. I know it sounds like a vacuum problem but what I am not sure about is that when the MAX AC is turned on and off the door on the passenger side kick panel opens and closes. If the door is open and I unplug the vacuum line at the selector the door slams shut and it will re-open when the line is connect again. Could this still be a bad vacuum line somewhere or maybe another component not working right, maybe the part that is supposed to open the door for the different vents?  

Answer
Hi
The best thing I could tell you is that check vacuum at all the vac. connections/door actuators both at idle and running down road.
Also check source vacuum(line off of engine). They should all be the same, eg... 13" of vac. on engine and 13" at the recirculate door actuator, etc...Also make sure yuo have good Vac. at the controller. Check the controller also.
If so you DO NOT have a vacuum difference, you MAY have an actuator problem or a binding mode door.
If your vacuum is different, eg.. lower at mode door, check for cracked line close to the battery where it goes into cab. Check for kinked lines around the engine cover(dog house) where it meets the cab, I've crushed them in there myself.
I would though, for your problem, suspect the Mode Door actuator, located on the drivers side of the case.
Hope this helps
JUST advice from experience.
Good Luck
Pawl