97 Civix defrost question
 

My Civic does not get any air through the dash vents. What can I check?
I can hear the air blowing, but nothing is coming out. I don't see
any obstructions in the vent opening. The air does come out the side
vents, just not to the windshield. Any thoughts? Short of tearing the
dash apart to get to the vents. Thanks.