Why is my trailer running lights not working?
Why is my trailer running lights not working? Because the most common reason for trailer lights not working properly is a bad or missing ground, check the trailer’s and truck’s ground connection first. A poor ground often becomes the culprit when only some lighting functions are working and when lights go out when you push the brake pedal. How do you check trailer lights? To test your trailer plugs, turn your multimeter to volt DC settings, then connect the black probe to the negative terminal and your other multimeter probe to one of the positive pins, and turn on the...