All about wiring a boat trailer

About US boat trailer and wiring a boat trailer

Trailer lighting is critical. Most light fittings are vehicle types with incandescent lamps although that is changing rather rapidly. They are easily flooded and waterlogged, with resulting burnout and failure. Many of you know what that is like.

Consider the new LED light types, they have significantly lower heat outputs and can be potted or sealed to reduce water ingress when launching and that will save you a lot in replacement costs. 

There are a number of trailer wiring and plug/socket configurations. The following are standard although you should check your own vehicle to be sure.

In the 6 pin terminal plug/socket the center terminal is marked A, and is an auxiliary terminal and is generally used for backup (reverse) lights. It is also used to supply +12 volts to charge the breakaway switch battery, which is common with electric braking on the trailer. This will help you if you are wiring a trailer or troubleshooting a fault

In the 7 pin terminal plug/socket 7 is the center terminal.

6 Pin Connector

Use the following Marking Codes, wiring colors and functions to help you. This will help you if you are wiring a boat trailer.

GD – White - Ground

TM – Brown - Tail Lights

LT – Yellow - Left Hand Turn

S – Red - Stop/Electric

RT – Green - Brake

A (Center – Blue - Right Hand Turn)

7 Pin Connector

This will help you if you are wiring a trailer 7 pin connector.

1 – White - Ground

2 – Blue - Electric Brake

3 – Green - Tail/Run Lights

4 – Black - Battery Charge +

5 – Red - Left Turn Stop

6 – Brown - Right Turn Stop

7 - Center – Yellow - Aux/Back up

Hint - It is best to attach the trailer wiring harness ground directly to the trailer frame.

Hint - The most common failure in trailer electrical systems is a bad ground connection. Really make the effort to keep them clean and tight.

Wiring a boat trailer - Flat 4 Wire Connector

This will help you if you are wiring-a boat-trailer flat 4 pin connector.

White - Ground

Yellow - Left Turn/Brake

Green - Right Turn/Brake

Brown - Tail Light

More about boat trailer parts and use this link to go back and find out more about wiring a boat trailer.