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

If you have a shop manual, there's a proof chart in there that shows what should be happening with whatever levers are selected

If not, you can download the 72 shop manual, but I don't know if 73's the same:

[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]

If that doesn't help I have a paper 74 manual, could post some shots.