Using the LED Electrical Trailer Cable tester is easy. This tester has one side to connect the 7 pin plug of a trailer and another side to connect the 7 pin socket of a car. The tester will indicate quickly if a failure concerns the wiring of the car or the wiring of the trailer. With an easy guide printed on top, pressing the yellow button on the side will illuminate the LED’s showing the effected function if they are working properly or not.
If the wiring is good, all the LEDs light up. If a LED doesn’t light up, it is because the corresponding wire is defective. If your tester reveals otherwise, see table below to find potential problem.