One brought up a good point, if you pull the inside cover there is a divider between the intake and exhaust, sometimes it's not installed correctly and allows the cool air to be drawn into the exhaust before it gets to the coach. Remove the filters on each side, there are four screws, one in each corner, remove those and the cover will drop down. The divider is a vertical flat plate kinda in the middle, make sure it's in place.
__________________
|