Why Would Trailer Wiring Only Ground Through Ball Mount on a Trailer

Updated 05/02/2016 | Published 04/29/2016

Products Featured in This Question

Peterson Combination Trailer Tail Light - 6 Function - Incandescent - Square - Passenger Side

(902)

$5.43

Hook Probe Circuit Tester

(67)

$14.06

Question:

The lights only seem to work when the trailer is grounded through the ball. The trailer is brand new, and it looks to have a nice new ground. But my question is the problem most likely caused by the trailer or truck ground when everything stops working when I disconnect the ball.

asked by: Kevin

Expert Reply:

Typically what you described is due to an insufficient ground on the trailer and not the vehicle. You can try running the grounds of the lights back to the main ground of the trailer and that should fix the problem. Or if the main ground strap of the trailer is attached to a painted surface you could try removing the paint and connecting it to a bare metal surface.

Or you can try testing the pins of the connector on your tow vehicle with a circuit test like part # PTW2993 using the ground pin on the trailer connector vs. attaching the ground to a metal surface on the hitch to see if there is a difference.

expert reply by: Jameson C