It's the dreaded 7-Way RV plug that we all have come to know and love. Most new vehicles equipped with a tow package have connectors. Trailers with electric brakes need them too. The 7-Way Trailer Plug is a round 2" diameter connector that allows an additional pin for an auxiliary 12-volt power or backup lights. It is usually used for towing a heavy-duty landscaping trailer, car trailer, boat trailer, horse trailer, travel trailer, construction trailer, and larger trailers

When referencing the 7-Way RV Plug diagram, make sure you are looking at the plug the way the diagram is showing you. Having the wires backwards will cause problems. Keep in mind that it isn’t always as simple as matching the colors like you might be inclined to do. Match the functions, not the colors. Make sure your ground wire, which is typically white, is securely attached to the frame on both the truck and trailer side. The ground wire should be large enough to handle the entire load, do not depend on grounding through the ball.

Grease your trailer plug. A thin coat of grease will help prevent copper oxide from building up. That is the green stu that forms when oxygen from the air or water come in contact with copper. You may thing the rubber caps protect the plug but they tend to hold the water in.

If your brake lights work, or your marker lights work, but nothing works when you turn on both at the same time, your trailer is not grounded to the truck. So, if you step on the brakes and all the trailer lights go out, then you need to ground your trailer to your truck with the ground wire.