[TechTalk]

The problem could be in any of the three wires: power, neutral, or ground. Consider whether any accessories have been added lately, such as an awning. A screw through a wire can do some bad things. Also, some of the coaches of this and earlier vintages were equipped with switches on the dash to turn the roof A/Cs on and off using relays, typically located in the front overhead cabinet. If you cannot trace the problem easily, we suggest you consider running a new power wire to the A/C, properly protected from a breaker, of course. In fact, the break in the connection could be inside a foam-filled wall, so a new power wire may be the only practical solution.