Harness Extender | etrailer Extend your factory harness to a new location or add a different style connector without having to remove your factory harness with this handy 3' extension. Features: Wiring harness extends your vehicle's 7-way RV-style trailer connector One end of wiring harness plugs into the back of your existing 7-way Other end hardwires into new connector Amazon: trailer harness extension Partsam Trailer Wire Extension Plug, 4 Pin Hitch Light Trailer Wiring Harness Extender with Rubber Cab for LED Brake Tailgate Light Bar, 32" Inch 4 Way Flat 4 Pin Universal Wiring Connector. by Partsam. $9 $ 9. 99. FREE Shipping. Only 8 left in stock - order soon.