On my 2000 Discovery I was having issues with cold air on both my ac units. I opened them up from the inside to discover that the material separating the warm/cold air exchange had fallen over. This allowed the warm/cold air to mix and my ac was basically sucking up the cold air and then repeating. I used hvac tape to fix the separating material, sealed it all up and instantly had cold air.
I also blocked off the forward ducts that lead to the space behind the old CRT tv. On my most recent trip to the beach I actually bypassed all the ceiling ducts on the front ac unit and let the air simply blow straight down. I could not believe how much cooler the front of the RV is now.
I then performed the same on the rear ac unit and blocked off the duct passage from the rear to the forward vents, forcing all the air to the bathroom and bedroom. It was an amazing difference and we actually have to turn the thermostat up to keep from freezing ourselves out in the bedroom.
2000 Fleetwood Discovery 36T
Living Life in the Foothills of East TN