Trailer Wiring Diagrams

Originally posted by BobWms at FarmBox message boards on April 19th, 2006.

Wire Installation Tips

By law, trailer lighting must be connected into the tow vehicle's electrical system to provide trailer running lights, turn signals, and brake lights.  This is accomplished by tapping into the tow vehicle's wiring harness.  Connectors are used between the two to allow disengagement when not towing.

Various styles of connectors are available with four to seven pins to allow transfer of power for the lighting as well as auxiliary functions such as electric trailer brake control, backup lights, etc.  Choose a connector that has the required number of pins for the functions required.  The male end (plug) is mounted on the trailer side and the female end (socket) on the vehicle side.

6 Pole Connectors - Sometimes called "Ranch Standard"

Round 1 1/4 inch diameter metal conductors are available that allow 1 or 2 additional functions such as back up lights and electric brakes.

6 Pole Trailer Plug, Round Pins.

6 Pole Trailer Socket, Round Pins

7 Pole Connectors - Sometimes called "RV Standard"

Additional pins for auxiliary power, trailer battery charging, etc. are available using larger 2 inch diameter round connectors.

7 Pole Trailer Plug, Flat Pins

7 Pole Trailer Socket, Flat Pins