73 Dart no air coming out of vents (A/C car)

73 Swinger went to use the A/C the other day changing from defrost setting and no air coming out of the vent. I pulled the vent assembly and noticed the air door in the box is staying closed not letting air into the vents. Pushing the levers back and forth the door does nothing. Feeling around under the dash i found a black vacuum line with a white stripe on it coming from the driver's side that wasnt attached to anything? any help would be great, thanks