How to Test a Trailer Wiring Harness
- 1). Connect the trailers wiring harness to a dependable vehicle's trailer connector.
- 2). Test all of the possible lighting sequences using a friend to observe the trailers lights. Apply the vehicle's brakes and confirm with them they are illuminating as required.
- 3). Turn on the right signal and confirm it's operational. Repeat for the left signal.
- 4). Turn on the vehicle's marker lights and check every marker on the trailer for proper illumination.
