2004 Chevy Avalanche Open vent for outside air, blows hot from 2 vents

I turned my temperature control knobs down to 60 as I wanted the outside cool air (62) to come through the vents.  On drivers side, the air came through hot, would not cool off, like the heat was on.  On passengers side of truck, air from vent was fresh and cool like outside.  Maybe door to heater core stuck open and allowing hot air through and not fresh? Would appreciate any help.  Of course warranty recently expired too.  

dang, that's interesting