Amazon: towing harness adapter LEDGlow Truck Flat 4 Pin Y-Splitter Adapter Trailer Harness - Powers Both Tailgate LED Light Bars & Trailer Lights. 4.7 out of 5 stars 200. $10 $ 10. 99. Get it as soon as Thu, Aug 8. FREE Shipping on orders over $25 shipped by Amazon. Reese Towpower 74682 7-Way Multi-Plug Connector. Best Trailer Wiring Adapter Parts for Cars, Trucks & SUVs A search for trailer wiring adapters near me shows multiple brands and wiring types. The most commonly used wire system is the three-wire system. There is a wire to the turn, stop and tail light that needs to be converted to two wires to connect to the single trailer light wire. So, there is a connector and a converter as part of these systems.