If I remember correctly, s few years ago the was an article in "MotorHome" Magazine which was either written by Mike or paraphrased by the author. I am mentioning this because it is something I have carried since it was published and I bought the test equipment listed in the article that were not already in my toolbox. So like Chris B, Mikes info is invaluable to me in the MoHo.
As a side note, my brother live in Mission Beach in San Diego and his neighbors quit coming over to his house. He finally ask why, was it the new screen door? Long story, but, there was an old screw that nicked a 120vac wire and while it was only wood involved, no problem, he installed a new aluminum screen door and now when it was foggy, 28vac to earth(damp concrete steps). Took me the better part of a winder day to find the flow of current was through salty moisture in the old redwood exterior trim to the aluminum door to earth.
Electricity is weird and independent, it will do seemingly impossible things. Buy the tools, use them and stay safe.