No air is coming out of center ac vents in 93 vw cabriolet how do you fix and yes they are on?

mine does the exact same thing, Your ventilation is operated on a vacuum system. when you open your hood, on the underside there is a black plastic piece that looks like balls grouped together, that is your vacuum system. you need to start there. follow all the litttle hoses and check there connections, and the hoses for leaks, if the hoses are old they often crack, and all you need is a small air leak for them not to work. I still cant find where my problem is, all my hoses are new, so good luck, if you have any in sight after post it here to help the next guy, i am a newbie You have to check the vacuum motor(s) under the dash - mine had the spring rot out & not function. The normal positon is spring on - vacuum retract (what you want to select). Parts cost $110 at dealer - you have to remove the upper dash cover - plan most of a Saturday. Remove radio / console / etc. first. This would be about an hour job IF the factory allowed for removal of the glove box. You can break off the plastic clove box tabs in the back of the cover & use 4x tinnermans & phillps screws to re-assemble. Glove box door covers everything & makes re-assembly easier too. Stupid design by VW