At this point, its exploratory surgery. You need to find the path to ground on that circuit. it can be anywhere from the lamps to the mlp.Maybe someone can help? I have a 93 f-250 with no reverse lights. I discovered the fuse was burnt out so I changed it and thought aha!Because they then worked.But that was short lived, a few days later they weren't working again. Must be a short. any suggestions?