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Trailer Wiring Tips

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Trailers are required to have at least running lights, turn signals and brake lights. To provide the power and a hook-up for these, the tow vehicle's wires are tapped into. This is accomplished through either a T-One connector (if available for your vehicle) or through hardwiring. The T-One Connector is pre-wired to a 4-pole flat that can adapt to a 6 or 7 way round connector. Hardwiring requires the installer to locate the proper wires in the tow vehicle. To help in this task consult the owner's manual or the chart at the bottom of the page.

Connectors

Various connectors are available from four to seven pins to allow for the transfer of power for the lighting as well as auxiliary functions such as electric trailer brake control, backup lights, etc. Choose a connector that has the required number of pins for the functions required. Also, mount the connector on the vehicle.  Not only will it display a clean look, but a mount is helpful in avoiding the potential problems associated with leaving a connector dangling.

4-Way Connectors
4-Way connectors are available allowing the basic hookup of the three lighting functions (running, turn, and brake) plus one pin is provided for a ground wire.


4-Way Flat Trailer Connector - *Most Common 4-Way Flat Truck Connector 4-Way Round Trailer Connector 4-Way Round Truck Connector

6-Way Connectors
6-Way connectors are available allowing the basic hookup of the three lighting functions (running, turn, and brake) and besides the ground, two extra pins are available to provide two additional functions.

 

6-Way Round Trailer End 6-Way Truck End 6-Way Square Trailer & Truck Connectors

The Diagram below shows the proper way to wire the connector to your trailer or vehicle.

 

Note: The black (12V) and Blue (Electric Brakes) may be reversed to suit trailer. Horse Trailers may use the center pin for 12V hot lead, R.V. trailers use the center pin for electric brakes.

7-Way Connectors
Besides the three main lighting functions, additional pins for auxiliary power, trailer battery charging etc. are available.

 

7-Way Trailer End 7-Way Truck End 7-Way Plastic Connectors.

 

The Diagram below shows the proper way to wire the connector to your trailer or vehicle.

5-Way Connectors
5-Way connectors are available allowing the basic hookup of the three lighting functions (running, turn, and brake) and besides the ground, one pin is available to provide support for another function. Usually the 5-Way Flat is used for trailers with surge brakes. The additional wire is tapped into the backup lights to disengage the trailer's brakes when the vehicle is reversing.


5-Way Flat Trailer End 5-Way Flat Truck End 5-Way Round Trailer End 5-Way Round Truck End

 

How to Wire 4, 5 or 6 Way Connectors

 

Wire Color By Manufacturer
Vehicle Manufacturer
Dual Purpose Bulb System
Wire Function Wire Color

   GMC

Ford Chrysler Jeep Toyota Honda Mazda

RIGHT TURN & BRAKE LIGHTS

Green

 Green

Orange W/ Blue Stripe Brown Brown Green W/ Yellow Stripe Green W/ Yellow Stripe Green W/ Yellow Stripe
LEFT TURN & BRAKE LIGHTS Yellow  Yellow Lt Green Orange Stripe Dk Green Grey W/ Black Stripe Green W/ Black Stripe Green W/ Blue Stripe Black Stripe
TAIL LIGHTS Brown  Brown Brown Black W/ Yellow Stripe or Black Blue Red W/ Green Red W/ Black Stripe Green or Black Stripe
GROUND White Black Black or Grey Black Black & Black Black or White Black Black
Single Purpose Bulb System
BRAKE LIGHTS Use Converter Pink or Lt Blue Red W/ Green Stripe White Blue W/ Black Stripe Green W/ Red or White Stripe Green W/ White Stripe Green or Green W/ Red Stripe
BACKUP LIGHTS Red Lt Green Black W/ Pink Violet Brown - - -
ELECTRIC TRAILER BRAKES Connect To Blue Wire From Brake Controller
Vehicle manufacturers have intermittently changed wiring colors over the years.
It is recommended that a circuit tester be used on the tow vehicles wiring harness to verify that the correct wire has been located for the proper function.