If you have a meter and know how to use one, now is the time to get it. Trailer lights are basically very simple to wire and get to work. Most of the time it turns out to be the ground wire that causes the problems. Start with where the trailer connector is attached and make sure those connections are good. Then work from there. Here is the standard trailer wire color code;
White-Ground (you can also run a white ground to each light for added assurance of a good ground)
Brown-Tail/Running Lights
Green-Right Turn/Brake - Remember green has an R in it
Yellow-Left Turn/Brake - Remember yellow has an L in it
Follow this and see if you can find your fault...
