Dash vents not blowing air. 2003 GMC Envoy

My wife recently started our 2003 GMC Envoy and heard a “pfffh” from the dash which makes think a vacuum line came loose. When she parked the car it wouldn’t start because the battery had died. I put in a new battery and now the dash board vents do not blow air. The lower vents, the defrost vents, 4wd, AC all continue to work. Thoughts

If the vents are vacuum controlled I agree and think you are correct.

Thanks. I think I may have found my answer here http://www.sparkys-answers.com/2009/05/2003-gmc-envoy-no-ac-vent-control-b0263.html

Interesting info you found there. I suspect you are on the right path to the cure.