How to Wire a 6-Pin to 7-Pin Trailer | It Still Runs Round connectors have circular holes for the same connection. Go to a hardware store and select an adapter that joins the two different types of wiring harnesses. Slide the 6-pin side of the adapter into the vehicle's harness by pushing the two together. Slide the 7-pin side of the adapter in the trailer's harness. 6 Pin To 7 Pin Adapter | etrailer This heavy-duty, coiled cable adapter is compatible with a 7-way RV blade trailer socket on the vehicle and adapts it to work with a 6-way connector on the trailer. Center pin on trailer side the tow vehicle's socket and the trailer/towed vehicle's plug. 47085 Hopkins Trailer Connector Coiled Adapter, 7-Way (RV Blade) to 6-Way. Wiring Adapters.