However, i use an adapter for flat to round when my trailer gets loaned out to a car with round socket. Below is a diagram for the original plug and socket showing the functions of each pin. wiring plug diagram a helpful chart and wire color key Details for small round 6 pin and 7 pin, flat 12 pin and flat 7 pin; Trailer plug wiring diagram 7 pin . 7 way trailer wiring diagram is explained in details in the picture and the table below: This is the 7 pin towing plug wiring diagram trailer flat light way and new of a imagine i get off the chevrolet trailer plug wiring diagram collection. This vehicle is designed not only to travel 1 place to another but also to take heavy loads. How to wire a 7 pin (12 n type) trailer/caravan plug. Wiring up a 7 pin trailer plug or socket is a simple and easy process, especially with the following step by step instructions and video demonstration provided.generally it is the same process with all brands of 7 pin trailer plug or sockets, howe...