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7,6,4 Way Wiring Diagrams

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7 Way Wiring Diagrams:

There are two wiring codes for different types of 7-pole plug and socket sets.

Most RV's use the RV wiring code for the type plug/socket that has 6 flat contacts surrounding a center round pin.  Semi's and commercial trailers use the ASME (American Society of Mechanical Engineers) type 7-pole plug sets.  These plugs have 6 round contacts surrounding a center round pin.

7-Pin Commercial Trailer Plug
Commercial Truck and TrailerWiring Diagram.

7-Blade RV Trailer Plug
Light Duty Non Commercial Truck, Fifth Wheel and Travel Trailer Wiring Diagram.

Note: the ways to convert from 7-Pin Commercial Plug to the 7-Blade Light Duty Plug is covered in Taillight Converters.

Truck trailer to RV Trailer

This drawing from Mark Bruss shows the relationship of the 7-round to 7-flat plugs and how only three wires are common.


6/4 Pin RV Plug
6 Way & 4 Way Wiring Diagrams

BTW, the wire colors on your truck or trailer could vary from the colors shown in the diagrams.


Brent at Otts Friction Supply on eBay is a good source for ASME Commercial Sockets, Plugs, Rubber Boots and other HDT related items.