Last weekend, I took the cover off of my A/C unit and noticed that it had probably been installed on a Friday afternoon. The gasket between rooftop unit and interior unit wasn't compressed, the separation between the intake and exhaust sides of the plenum was not taped, and there were open spaces where air could go right into the insulated space between roof and ceiling. I spent a couple of hours with a big roll of aluminum foil duct tape, sealing everything up. I torqued the four bolts holding the top and bottom sections of the unit together. I took down every vent in the coach and re-taped the openings, smoothing down anything that had lifted and adding tape in areas where it was too short. I taped the seams where the squirrel cage fan joins the exhaust plenum. I sliced my thumb open on a sheet metal edge and bled like a stuck pig (should probably have worn gloves).
The end result is that the unit's airflow is improved by about 40 percent, and it cools much better than ever. It's also quieter. My next task will be to make a sheet metal baffle to better direct air from the squirrel cage fan into the ductwork. On my unit, the ducting only comes off of one side, so it should be pretty easy.
I'm wondering if otrfun's coach has similar problems in the factory A/C installation.
