My 07 Cherokee 32B had the opposite problem. The bunk room was like an oven! What I did here was block about 2/3's of the vent. This forced the hot air back out through the other vents.
Do you feel anything coming out of the vents? Maybe you will need to block off another vent to force the heat back there. Just takes some time and patience.
2012 Georgetown XL 350TS, Hellwig front/rear sway bars, Sumo Springs, Blue OX True Center steering damper
2013 Ford Explorer LTD toad, Roadmaster Stowmaster 5000, VIP><Tow Brake
Better to have a bad day of camping than a good day at work!