I have an 05 QC hemi 5.7 and just experienced a problem with trying to change from air blowing at me from the dash vents to the defrost mode. There is no change and just continues to blow air at me. It's going to get a little hairy when we start getting cold mornings. Does anyone have an answer to this problem ??? I thought it might be a vacuum leak but I'm not sure if this system uses vacuum or is it electric.