How to Wire a Trailer Harness From 7 Way to 4 Way

by Bob White

A 7 way trailer system provides power for signal lights, marker lights, brake lights, powered breaks, batteries and back up lights. By reducing it to a four way system you are eliminating the powered brakes, batteries and backup lights. If these systems are necessary for safe travel you should reconsider this modification. If you have consulted your vehicle's manual and have determined it is safe to tow the trailer without the powered brakes, changing the harness over to a 4 way system can be done in an hour.

Cut the 7 way harness off the trailer using the cutting tool on the wire strippers.

Strip the green, yellow, white and brown wire back 1/4 to 1/2 inch. Also strip the wires on the 4 way trailer connector in the same fashion.

Connect like colored wires together using the butt connectors. The butt connectors work by inserting the two wires into each end of the connector and compressing with the pliers. Assure a tight fit by gently tugging on the connection.

Wrap each connection in electrical tape then wrap all four connections together providing additional protection against the elements.


  • close Reducing a 7-way system to a 4-way system eliminates the powered trailer brakes, batteries and back up lights. These systems may be important for safe operation of the vehicle and trailer.

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About the Author

Bob White began his writing career in 2006. Working in sales, he was a technical writer tasked with responding to requests for proposal. White has a Bachelor of Arts in computer science and a diploma in home inspection. He has also worked in construction, landscaping and the pool industry for more than 15 years.

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