A/C Question

I have a 1997 Town & Country LXi. The A/C system (front and rear) blows cool to cold air pretty good however, the rear overhead vent behind the drivers seat blows warm air while all others are blowing cold. All components of the A/C system check out ok and the vent in the cargo area that draws in the air is not clogged or obstructed. Can anyone shed some light on this anomoly? Thanks.