I agree Bob, but here's my reasoning on flipping the breaker on the converter.
The AC worked fine when sitting on the floor. At this point I'm assuming the AC is the only load on the circuit.
Once he puts the AC on the roof, everything else in the trailer can draw off that same 15 amp shore power line.
Although not quite the same, my experience is dry camping with my Honda 2000i generator. With low batteries (a night of heater)the generator will usually run either my microwave or the AC. But only if I shut off the converter. If the converter (or even the refrigerator on auto)is on at the same time, the microwave runs slow or the generator overload breaker blows with the AC.
So by shutting off the 40 amp converter, I remove a load off the generator and the microwave runs normal and the AC doesn't trip the overload breaker.
So while it's not the same situation, his the converter is putting a load on the system that wasn't there when the AC was just sitting on the ground Plus the test is free and you don't even have to get on the roof to run it. It only takes a minute to throw all the breakers and remove all the load off the shore power. Then either the AC runs or it doesn't
