Using a swamp cooler

eHoefler wrote:
A/C remove humidity to cool, you would have the 2 different systems fighting each other and will get nowhere. If you adding a unit, add an A/C

A/C "chills" or "cools" the air going through the coils and as a side benefit the chilled coils removes some moisture in the air as the warm moist air flows through the cold coils and condenses out some of the moisture which drops to the catch tray and out of the A/C unit.

A/C also reuses the interior air so each pass through the A/C unit more moisture gets removed. Each time cycled through the A/C unit the air coming out will get cooler since you are not adding outside hotter air.

OP has several ways they can go if current A/C is not cutting it. They could replace current A/C with a higher BTU unit, most RVs typically are outfitted with 13.5K BTU A/C units which in larger RVs may be marginal at best.. a 15K unit could be used instead provided they have enough amperage capacity on the shore cord..

A second 13.5K BTU A/C unit could be installed provided they have an extra roof opening to use and have a "50A" shore connection..

They also can of course attempt to find a nice shady spot under a canopy of trees.. The air temps under a good dense canopy of trees can be considerably cooler than if one was out in the open to direct sunlight.

But mixing refrigeration A/C with swamp cooler isn't going to work..