The unit pulls the inside coach air through a filter media and across the evaporator coil. This area is the return. The heat in the air is removed and is then pushed back into the coach. This area is the discharge side. If you remove the ceiling assembly, or in some cases pull the roof unit off for those that have separate return ducting, you will see these ports. These must be sealed from each other or the evaporator coil will freeze up if the air is short cycled back through.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7