Mini Split Air Conditioner AmericAire 120000 Heat Pump
They are not specifically designed for RV's but a quick search and you will find plenty of folks "down under" who have retrofitted them on Rvs with great success. They have extreme heat and also extreme rough road conditions in Australia, so I consider that a good testament to the durability.
What gets me going is the lower power draw of the 12,000 BTU units. It is 2/3rds of the rated draw of a typical Coleman 13,500 BTU unit. I suspect that a Honda EU2000i generator just *might* be able to start it.
The other huge bonus is when you are plugged into a full hookup situation. Now you have a 12,000 BTU heat pump, also much more efficient. Keep that propane in your tank.
In your case you would hang the outdoor unit on the back, find a suitable wall and route the line set and cables, and finish off with an Rv skylight to fix the hole where the old AC was.
RV Skylight
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2007 Dodge Ram 3500 SRW 4x4 with 6MT
2003 TDI Beetle
2002 TDI Beetle
currently parked - 1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears