Ok lets try this a diffrent way.Is there any way to bypass a vacum line a/c,or at least trick it to get the dash vents open.

Do you have a vacuum leak at the dash control? Are you getting any air from anywhere (defroster/floor/etc)?

I had a problem where none of my HVAC functions worked from my dash. To it to the repair shop, they determined it was a bad vacuum line, which sounds like what TommySS is talking about. They replaced the vacuum line and it worked fine afterwards.

Try turning on the vents then switching back and forth to defrost and etc and listen for a leak.