7-Way refers to the seven-terminal receptacle, electrical cable, and plug system that transfers power from a tractor to a semi-trailer. The system consists of a seven-terminal receptacle on both the tractor and trailer, connected via a cable with a 7-way plug on each end.
Trailers used as a part of double and triple trailer formations have receptacles at both the front and rear of the trailer to provide interconnection between trailers and dollies.
Standardized Tractor-Trailer Connection
In North America, the trailer receptacle and cable are standardized to ensure compatibility between all tractors and trailers. SAE International has identified this standardization as J560.
SAE J560: Primary and Auxiliary Seven Conductor Electrical Connector for Truck-Trailer Jumper Cable
This SAE Standard provides the minimum requirements for primary and auxiliary jumper cable plug and receptacle for the truck-trailer and converter dolly jumper cable systems for 12 VDC nominal applications. It includes the test procedures, design, and performance requirements. The color of wiring insulation for each trailer circuit is also standardized.
|SAE J560 Standard Wiring Colors for Trailers|
|WIRE COLOR||LAMP & SIGNAL CIRCUITS|
|White||Ground return to towing vehicle|
|Black||Clearance, side marker, and license plate|
|Yellow||Left-hand turn signal and hazard signal lamps|
|Red||Stop lamps and antilock devices|
|Green||Right-hand turn signal and hazard signal lamps|
|Brown||Tail, clearance, side marker lamps, and identification lamps|