Does your a/c blow cold? or do you have poor/low air flow from the ducts? I have a 2015 Eagle 345BHTS and had very low duct discharge pressure, it turned out to be rubber roof material blocking 3/4 of the duct opening at the a/c unit. The factory runs roof material over entire room, a/c guy trims excess roof material to mount a/c he did a crappy job by not trimming roof material well thus blocking both duct runs. Dealer will not look that hard to find this problem, I took entire unit apart to find this. hope this helps.
2015 345 BHTS 5th Wheel
2005 Chevy 2500HD Duramax Diesel