Stephen, I have a 2018 Fleetwood Pace Arrow 38N and I too have and still have problems with my Dash AC. I took mine to an Oasis Dealer and they check all of Freightliner components and they were found to be working as advertise. They found the problem is in the box in front of the dash, Fleetwood knows this to be a problem per the Freightliner techs. My cooling unit would freeze up, and I was only getting luke cool air. They found a thermostat on the upper right side (looking at the box) and felt it was in the wrong place. Fleetwood said to move it to a hole in the front, kinda the middle and to the left. It was duck taped in place and the air was cooler, but still not what I think it should be.
If you want pictures, I will see what I do, and if you find a cause, please let me know.