[PDF] Trailer Wiring Diagrams - Tractor Parts Online UK Trailer Wiring Diagrams Here are the wiring diagrams for UK 7 pin & 13 pin sockets or plugs. The 7 pin standard trailer socket, it also covers the wiring of any UK trailer and most European standard 12n wiring. The views are from the rear as you look at the terminals to wire the plug or socket. In all cases the terminals will be numbered. 7 pin 'N' type trailer plug wiring diagram | UK-Trailer-Parts Here are two wiring diagrams for the 7 pin ‘N’ type trailer electrical plug. The first diagram is a simple set up of two brake lights, two indicators and two side lights. Click on the image below to enlarge it. The second diagram shows two brake lights, two indicators, two side lights and a fog light. Click on the image below to enlarge it.