Amazon: 4 pin trailer connector SUZCO 25 Foot 4 Wire 4-Flat Trailer Light Wiring Harness Extension Kit, 4-Way Plug 4 Pin Male & Female Extension Connector & Wishbone-Style with 18 Gauge White Ground Wire with SAE J1128 Amazon: 4 pin wiring harness CZC AUTO Trailer Wiring Harness Kit 4-Way Wishbone Style, Y Style 18AWG Pure Copper Core Color Coded Wire with Standard 4-pin Flat Plug Connector, 4' Female and 25' Male for 12V Trailer Boat Marine 4 Pin Wire Harness Connector, 4 Pin Wire Harness Connector Alibaba offers 4,564 4 pin wire harness connector products. About 50% of these are connectors, 40% are wiring harness. A wide variety of 4 pin wire harness connector options are available to you, such as electronic, motorcycle. How to Install a 4 Wire Trailer Light Connector | It Still Use a wire splice to attach the brown wire from the four wire trailer light connector harness to the brown tail light wire. Step 9. Drill a 1/8 inch hole in an exposed section of the metal frame inside the trunk. Use sandpaper to sand the metal within about 1/2 inch of the 1/8 inch hole. How to Wire a 4 Pin Trailer Connector to a 7 Pin Connector How to Wire a 4 Pin Trailer Connector to a 7 Pin Connector by Jack Hathcoat . There is a lot of competition and confusion in the trailer world when it comes to connectors. Cut the four-pin plug off of the trailer harness. Verify the harness color codes at each tail light.