OK, as Spock would say - Logically it will not work -- not enough space being shaded (as Will mentions above). However, illogical as it may be, it does. By keeping its own case cooler, the unit is better able to cool the coach. Think about it this way -- you are standing out in the sun with a mild breeze. Still hot; now step under a cover (even an umbrella). Same hot breeze blowing but you feel cooler. The suns radiant energy is not heating you now so the body is able to use the breeze to cool you more efficiently.
By the way - this is not an original thought -- I just had to have the air conditioner (heat pump actually) replaced at my stick house and the installers talked me into moving my outside unit from the west side of the house to the north. Same explanation -- the afternoon sun was striking it directly where it is now somewhat sheltered. Guess they were right -- the unit sure cools the house nicely
and runs much less time doing so.