i'm also having this problem (on an 06(dodge)2500)
no air comes out of the windshield/defroster vents, no matter what settings, no matter how fast the fan.
is there a precise setting of the knobs that does the trick, or does the control system (cables, vents, flaps) have a problem?
reason i ask about this, is the manual is somewhat less than clear (to me) about how to set the knobs to get airflow onto the windshield
the guy at the local dealer said something to the effect that: 'oh yeah, have seen that before, had to take the entire dash/console apart to fix it, cost appx 2000bux'
HUH?!! (getting the idea these things are like a B.O.A.T. = 'Bring Over Another Thousand'
any insights on this one very much appreciated (esp since we got the white stuff up high this morning and time grows short to work outdoors)