Since you have a 30A coach, odds are you also have an Energy Management System (probably Intellitec)that prevents both a/c's from running simultaneously. It will let the fans run, but usually won't allow both compressors to cycle at the same time. That's because 30A is not sufficient to handle the starting load of a second a/c while the first is running.
Usually such coaches are wired so that the generator can supply both a/c's and run them both. The generator capacity is usually greater than 30A and one 20A circuit from the generator will supply the rear a/c while the main 30A circuit powers the rest of the coach, including the front a/c.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL