I no longer understand how electricity works. I always thought I had a fairly good grasp of the flow of electrons, resistance, conductivity, etc. After working on my TT today I found out that I don't know squat. I had two outside lights that never worked so I went and bought a couple new patio lights to get them all working. I installed them and guess what - they didn't work. I pulled everything apart again and tested the wiring. On one side was a yellow and green wire attached to the black on the light. There was a white one attached to the white from the light. This should be simple - I checked the voltage from the yellow / green to the white. Nothing! Then I checked to the frame. The yellow and green both showed 13.05 volts to ground. I then checked the white and it too had 13.05 volts to ground. All 3 wires were hot. Bare in mind that this is on a fiberglass pannel that has no conductivity to ground. I then went to the courtesy light by the water and power hookup. I found the same situation with the green, yellow and white wires. The only difference is that this is on the aluminum skin so the fixture is grounded. I now am clueless as to what is going on.
I now have a new "Doug's Law" it is "If it works leave it alone. If it's doesn't work leave it alone and put a fuse in it so you don't burn the trailer down some night"

Doug, most people have no idea of how electricity works. Have you read the Dark Sucker post by Bill H? That should "enlighten" you.