Location if AC Dash Air Drain 06 HR Navigator??

I think you guys may be indirectly solving my own dash AC problem. I have a 2005 Coachmen Santara MH and the dash air isn't blowing cold. Had it checked this week by a local garage and they say the AC unit is blowing cold but something is preventing that air from getting to the dash ducts.

I'm wondering if I have a blockage in the drain hose that has backed up and preventing the cold air from getting through?