Try it on Max AC this cools air from inside the RV that is drawn from a duct under the front dash by the floor on the passenger side.
When idling the air temp at the fresh inlet under the front cap in front of the radiators increases by as much as 30 degrees F and so the AC is now cooling much hotter air. In the worst case the air coming out of the dash vents can be hotter than the current air inside the coach.
When on recirc the air being cooled is from inside the RV so this effect is avoided.
Once I figured this out I now just use Max AC all the time.
Randy - Manhattan, Kansas
2015 Vista 27N
2016 Honda HR-V