Retail websites that specialize in trailer parts, such as eTrailer, and vehicle enthusiast websites, such as The Ranger Station, are two great places to find information about wiring trailer lights. Information on these sites include wiring diagrams, wiring color code charts and detailed connector descriptions.
Connectors for trailer lights range from a four-way to seven-way connection. Each connection point above four handles an additional feature of a trailer, such as electric or hydraulic brakes. Connectors can even power lights inside a trailer. Each wire color is responsible for exactly one function of a trailer. Although the connection points are the same for the interior wiring of a connector, exterior plug sizes for connectors can vary from vehicle to vehicle.