Troubleshooting Trailer 7-Way Wiring Where Only Running Light Circuit Functions

Question:

Big Tex trailer with 7pin connector - lights come on/off, but brake lights, turn signals and emergency flashers dont operate when initiated. I have cleaned the pins and plug with white vinegar and rubbed with 180 grit sand paper. wiring looks ok to/from each side - thoughts?

asked by: John M

Helpful Expert Reply:

I would get a circuit tester like the part # PTW2992 to test the pins on the vehicle side of the wiring for voltage when the various taillight signals are applied as this will tell you if the problem is on the vehicle or trailer side. If the voltage is on the pins correctly it's the trailer but if not it's the vehicle and you'd need to basically trace wires to find problem and fix as needed. You can also check the fuses under the hood as that can sometimes be the issue as well.

expert reply by: Jameson C