Trailer Wiring Diagram - Wiring Diagrams For Trailers The trailer wiring diagrams listed below, should help identify any wiring issues you may have with your trailer. When shopping for trailer connectors remember that the male end is mounted on the vehicle side and the female on the trailer side. Trailer Wiring Videos.How to Wire a Trailer · 4-Way Trailer Connectors · Testers and Test Equipment · Wiring Components Trailer Wiring Diagram – Lights, Brakes, Routing, Wires The following trailer wiring diagram(s) and explanations are a cross between an electrical schematic and wiring on a trailer. We recommend these standards because they are pretty universal. That said, for specific situations, there are industrial standards with different connectors and wire arrangements.