Volvo Repair: A/C Blower problem, vacuum problem, selector dial

Question
89 760 DL Turbo, When the selector dial is on auto, the AC only blows out of the 2 very side vents that blow at the side windows, when I use the fan selector dial, the fan speeds up but no air out of the dash vents, only the very 2 side ones.  Air is nice and cold but not in my face.  What should I look at?

Answer
it could be a vacuum problem or a problem in the control panel.this system is somewhat complicated with too many moving parts.most common is the vacuum distribution block behind the passenger glovebox area.it usually gets bad solder connection at the back side of it.