I plugged my (new to me) camper in to an outside receptacle last week and all was well, all lights, appliances, and radio worked without a hitch. Last night I plugged it in to the same receptacle again and....pop! Tripped the breaker. Nothing has changed since last week, the camper has not moved, the batteries are charged, no wires look frayed anywhere. Everything works fine when running on battery power. I switched all of the breakers in the camper off and it still trips the house breaker instantly. I would have to assume that a hot wire coming into the camper has become grounded (ghosts maybe?). I have no idea where to look for this short. Cable coming into camper is fine, bought new 30A to 15A adapter and 10awg 25ft extension cord, opened junction box and all looks good, romex out of box looks good, pulled the breaker box out of the wall, everything looks good behind there too. I have a decent understanding of electrical circuits, I was an auto mechanic at one time. I would check for voltage but it won't stay on at all. I checked for continuity at the box and found the hot wire to the breaker for the camper receptacles is showing 2.5 ohms of resistance between common ground, is this normal? None of the other hot wires are giving a reading, they are OL, as I would expect. Does this mean that specific wire is grounded somewhere? Could it be a faulty receptacle? How could this still happen with the main breaker off? Thanks in advance for any advice, I'm ready to start tearing out walls to find this short.