I have a short somewhere in my trailer lights. I have a four prong, flat plug setup. When I plug them in, the fuse in the truck for the trailer parking lights blows - turn signals work - all marker lights and tail lights are out. With the plug disconnected from the truck, a meter shows a short in the parking/brake light line at the plug. Can't find any bare wires touching the trailer. Have disconnected all bulbs - still shows a short. Any ideas would be appreciated - I know I may have to rewire the trailer.