vent control inop

I have a 1996 Buick Park Avenue Base the AC and mid fan setting do not work. Sounds crazy but was in a car wash one day and the mid vent just started working out of no where... (Quit after exit) I feel like this is caused by a vacuum line, or blockage. I saw a similar post on forum some time...

Ok so I have a 1998 Regal LS nonSC Auto Was having problems with A/c blowing weak at the dash vents and I thought it was the Passenger Air scrubber. I replaced it as I couldn't remember when it was last done. Didn't solve the problem but the air smelled better (no more rotting plant life). So I...