There are a wide variety of trailer connectors. They can include anywhere from 2 to 7 wires. The type you use will be determined by the needs of your vehicle and trailer. Here we will cover some of the most common types. Below is a diagram of the typical 4 or 5 way trailer wiring. You should always confirm the actual wiring of your trailer before making a connection. Never assume the trailer or your vehicle is wired according to standards.
4 Way Trailer Connectors:
4 Way trailer connectors are very common. They can handle the needs of basic boat and utility trailers. The allow for the hookup of three lighting functions – running lights, turn signals, and brake lights. Both flat style and round style connectors are available as 4 way. There are adapters available to adapt a 4 way wired trailer to a 7 way wired truck.
5 Way Trailer Connectors:
5 Way connectors handle the same lighting functions as 4 way and the extra wire / pin is available to handle another function. Typically the 5 Way connectors are used for trailers with surge brakes – the additional wire is tapped into the backup lights to trigger the disengagement of the braking system. This type of wiring is less common now and if you are wiring a trailer, you should consider wiring it to the more common 7 way plugs.
6 Way Trailer Connectors:
In addition to basic lighting functions, 6 Way trailer connectors include two extra wires/pins. Typically these are used for electric brakes and a 12V power lead. 6 Way round connectors are commonly found on horse trailers, whereas the flat style are seen more on campers. This type of wiring is less common now and if you are wiring a trailer, you should consider wiring it to the more common 7 way plugs.
7 Way Trailer Connectors:
In addition to basic lighting functions, 7 Way trailer connectors have three extra wires / pins. These can be used for electric brakes, 12V power, and backup lights. Round pin connectors exist, but are uncommon. Most feature flat blade type connectors. This is the most common style now wired onto new vehicles. You can get an adapter that will adapt your 7 way wired vehicle, to a 4 way wired trailer.