OK Robert, but remember on a 30 plus year old trailer it may have been changed. Originally there were two wire cords that came out of the tongue, one on each side of it at the front. One cord was for the left tail / stop / turn light
and left marker lights
. Other cord did the right tail / stop / turn light
and right marker lights. If you still have those original wire cords you want to examine them closely, especially under the trailer because with age the rubber covering can crack and bare wire can be exposed. The reason for the two wire cords is that Uhaul
had special tail light
bulbs they would install in the rental customers vehicle , those bulbs had short wires attached that the trailer wires would plug into. Tap-A Light is what they were called. For modern vehicles where you have a 4 wire flat plug you can connect the appropriate wires on the trailer to a matching 4 wire plug. Or what I did was take it all out, run my 4 wires from the tongue back under the trailer, up inside below the closet, back to the right tail light, then across the rear inside to the left tail light. The marker light wires usually drop down on the center of the trailer sides, by the closet and under the sink area. Another odd thing, assuming you have the original tail lights
is; the upper bulb (amber section of the lens) is for the turn signal and is a two filament bulb socket, but only one filament of the bulb is used so one wire does not get connected.