Debugging Trailer Electrical Issue

Sometime near the end of our last RV trip, most of the electrical outlets in the trailer stopped working. Most but not all. And just about all of the outlets are on the same breaker. But some that are on that breaker still worked. This means a wiring problem. When I pulled the breaker panel, there was only one cable which went to the automatic transfer switch. And only one cable returning from the transfer switch to the electrical panel. From here, it branched out to two cable runs. One went to the TV, which worked fine, and one to the outlet that we plugged in the heater, which also worked fine. Also, the outlet on the ceiling of the bedroom worked fine. But the other outlets in the bedroom, the GFCI outlet by the sink, the kitchen convenience outlets, and the outlets on the rear wall of the trailer did not work. The refrigerator outlet, which is also on the same breaker, continued to work. It turns out that the outlet on the bedroom ceiling was a "hub" as it had three cables. Ont to the bedroom outlets, and one to the refrigerator. The bedroom outlets continued on to the GFCI outlet. From there, it daisy chained its way through the kitchen, the external outlet, and the outlets on the rear wall.

RVs use these odd outlets that are kind of designed for retrofitting into walls. Here is an image of the rear. Unlike regular household outlets, these are designed to just lay the Romex into the three slots then force the rear cover on which pushes the wires into metal slots which cut through the insulation and make contact with the copper wire. Convenient but not a lot of load carrying capacity. It worked fine with the kitchen appliances but when I plugged the electric heater into the last outlet on the long chain, that's when it failed.

I knew that it was a bad connection somewhere as I was still measuring 118VAC between hot and ground but only 12VAC between hot and neutral. Between neutral and ground, I was measuring about 95VAC. So things haven't completely failed. I pulled a couple of outlets including the refrigerator, one of the kitchen convenience outlets, and the bedroom ceiling. I think these weird RV outlets are only designed for two cables and not three. I used wire nuts on the ceiling cables and a short wire for the hot, neutral and ground for the outlet itself and all of the outlets are working once again. The 12VAC is still a bit confusing. Where is that coming from? I removed the GFCI outlet, no difference. Odd.

Of course, working on the RV is just an excuse to not work on the front porch...