Got the light to work but it's a booger. So here's a few things I learned.
Two wires go into the light fixture but only one is needed which is the hot 12V
wire. The body of the trailer is the ground and it needs to be cleaned to make a connection. The socket itself was rusted on the base. I took it and scrapped it with a wire brush inside and outside, then sprayed WD40 on it. The base of the socket still worked but needed some TLC. I have no idea what the wiring color scheme means. A wire may start out black at the wall switch and then be white or red at the light socked. I never know which is the hot wire by color. Use a volt meter and set it to DC (mine to 50 scale) to read 12 volts. Using the ohm meter to track down a wire for continuity is essential. I tracked the wires from the light to the door side switch. There was no 12V
there at all. Had to locate the hot wire on the switch for the outside light. Then drill a hole through a metal brace to pull a new wire over to the switch by the door with a coat hanger. Also have spare SFE 12V
20 amp fuses handy, you'll need them.
Get them at an Auto parts store, don't waste time at Lowes or Home Depot.