Restricted airflow due to duct collapse, and the freeze sensor not installed in the coil.
Defrost coils, install foam braces inside every AC register, and re-install freeze sensor.
What we have here is a frozen evaporator coil. The customer called with complaints of the AC’s not cooling well. This being the first time pulling his brand new camper from home, the customer was justifiably agitated at the situation.
We discovered that every single return and discharge vent in the entire camper was all but completely suffocated due to the foam ducting collapsing directly at each inlet / outlet. The solution was to cut some foam braces to get the customer up and running more efficiently. This greatly increased the cooling efficiency in one of the AC’s, however the other was discovered to be completely frozen. Circled in the picture, you’ll see the thermistor (freeze sensor) laying down by the control board. This sensor had tape on it, as if it had been taped to the side of the coil rather than pushed through the fins perpendicular to the coil. Once the unit was defrosted and the freeze sensor put back in, the trailer cooled down as it should.
This long winded synopsis can be used as a warning to potential camper buyers. Hire an NRVIA inspector, or at least inspect for yourself, and do a thorough run through of each system to ensure what you are purchasing is ready to hit the road. This goes for new campers as well as used.