7 Wire Diagram for Trailer Plug | Printable Diagram Check out 7 Wire Diagram for Trailer Plug for a quick reference on trailer wiring. 7-Way trailer connectors are found on most recreational vehicles and are used on a larger gooseneck, 5th wheel, boat and utility trailers. There are two types of 7-way connectors.[PDF] 7 Way Plug Wiring Diagram - Country Trailer Sales 7 Way Plug Wiring Diagram Standard Wiring* Post Purpose Wire Color S Trailer Electric Brakes Blue GD Ground White A Accessory Yellow This is the most common (Standard) wiring scheme for RV Plugs and the one used by major auto manufacturers today. * Always test wires for function and wire accordingly. This wiring scheme is for reference only.