Why does my A/C jusy blow out the defroster vents?

[ToocoolZ28]

The A/c in my 89 Camaro just blows out the top defroster vents. Is there a way to fix this or at least jerry rig it so the the air will come out the lower dash vents?
Thanks
Ron

To the mods, I posted this in another section also, I didnt know where to put it .
Ron

[Jeremy]

There should be a purple vacuum line (among other colors) going into the back of your HVAC control head. Check for vacuum on that line. You could have a break in the vacuum line in the engine bay somewhere or under the dash. I'd also check that black vacuum reservoir (looks like a ball) and make sure a vacuum line is attached to it.

[ToocoolZ28]

Thanks Jeremy, there is no vacuum on the purple line, or any of the others either on the heater control. I have tried to trace the lines in the engine compartment but couldnt follow them all the way. Do you mean the big black ball under the left front fender? Can it go bad or develop leaks?
Thanks again.
Ron