Center Vents air flow fixed - not under dash!
 

We got the dreaded 'center vents don't work, AC blows out the defrost vents' syndrome last week. After searching the archives, we were expecting big bucks to replace one of the deeply entombed vac pod elements or other under dash components that went bad. Fortunately, we got lucky: The tech pulled the glove box/airbag unit and checked vac at the manifold in the dash, and traced it to a vacuum line problem under the battery tray and to the vacuum reservoir. He removed the inner fender liner, replaced the vac lines, and we were good to go.