So.....I'll give you my experience with our AC (and we live in AZ). So after complaining to the dealer about the A/C being worthless, they checked the plate between the cold air and return air at the AC (where the cover is). They taped it off as to make sure the cold isn't being sucked into the return air. It worked...... but not all that good. So after still not getting the cooling I thought it should be doing, I did a little probing myself. I took down all the vent registers and stuck my phone camera up into the ducting. What I found was kinda funny but not, the foam ducts extended the length of the ceiling, past the last vent. So I bought some foam sheets and cut them to the size of the ducts, taped them into place with some AC foil tape at the duct. Both ends of the coach. The other place where it seemed to be loosing cool air was around my roof vents. I could touch the frame work and they were quite cold! Come to find out, the rear fan opening was set up for a second A/C unit (wiring and such). So I again, cut pieces to cover the A/C duct opening at the fan. At the end of each vent I closed off around 2 to 3 ft of ducting so the air was now being directed right to the vent. We find that after closing off the extra ducting with foam and taping it closed, we now have a pretty good amount of cold air going to all of the ducts now. Made a big difference in being able to cool the entire coach.
2017 Thor ACE 29.3