Types of Electrical Trailer Connectors

by Justin Mitchell
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Trailers are very simple machines, but the most complex part of them is probably the electrical connector, which allows the signal lights to the trailer to work in concert with the vehicle that is towing it. Many different types of connectors are in use today. They are defined mostly by the number of pins that they have. Usually, trailer connectors come with four to seven pins. Usually the more pins a connector has, the more functions that connector can facilitate. It's a good idea to understand the different types of connectors before buying a trailer.

Sockets and Plugs

Electrical connectors can be split into two broad categories, plugs and socket. Plugs have the openings for the pins on them, but do not contain the actual pins. The sockets contain the pins, and they are usually mounted on the trailer itself.

Four-Way Connectors

Four-pin connectors, also called four-way connectors, allow for the most basic functions in a trailer, such as running lights, turn signals and brake lights. One pin is for each function, while another pin functions as a ground. These connectors can come in several different configurations, including flat and round connectors. Four-way round connectors are the most common type of trailer connectors.

Five-Way Connectors

Five-way connectors provide electrical connections for each of the most basic lighting functions on any trailer, one pin for a ground, and another that is able to facilitate another function. Usually, this other pin is used for a feature such as surge brakes or hydraulic brakes. These connectors come with an extra wire that is tapped into the vehicle's backup lights so that the trailer's brakes will be disengaged when the vehicle is put in reverse. These connectors also come in flat and round configurations.

Six-Way Connectors

Six-way connectors provide for the basic running, braking and turn signals, plus two more functions. Usually these functions are electrical brakes and a 12-volt "hot" lead. These come in two configurations, flat and round. The six-way round connectors are commonly found on horse trailers, and the six-way square connectors are commonly found on campers.

Seven-Way Connectors

Seven-way connectors provide for the three basic functions of the trailer's lights, the electric brakes, a 12-volt "hot" lead and another one that is usually used for backup lights. Seven-way electrical connectors usually come in two major types, one with flat pins and another with round pins. The flat pins are usually referred to as blades. The round pins are rare. Most RVs have a seven-way connectors with flat pins.

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