To all: Thanks for the suggestions. Got the coach back today from RV World in Nokomis FL. It was the separated duct! I checked it before, but the break was about 3 feet up inside the rear cap. The tech could not even reach it. He had to use a piece of wood to apply the tape.
I also asked about the inside coil cleaning on the 38J. He said that you remove the outside panel and use "coil cleaner" that you can buy at Home Depot and use a hose with a moderate amount of pressure. He said that this also works on the outside coils and he recommended it be done every six months of cooling.