I final convinced my dealer after having camper for a week that there is not enough air flow. They tried to tell me was working fine with 82 return and 53-55 supply. I own an air conditioning company, I had to explain to them that won't fly. Factory is no help so far, told they what they need to do, increase return, mine has ducted return and supply. It is way too restrictive, gave them two options in my opinion they can install return below unit like they used to be or tear off roof and rebuild. Factory tried to blame Coleman, they concurred not enough air flow. Dealer is getting new returns to add while they wait days for response from factory. I've read too many posts about this same issue to believe factories are unaware of the problem by now.
2017 Columbus 377MB pulled by 2016 GMC Denali 3/4 ton