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Troubleshooting Intermittent Trailer Light Operation When Coupler Moves on Hitch Ball  


Trailer lights blink off and on when trailer shifts on hitch.


Expert Reply:

From your description of the problem - your trailer's lights blinking on and off as the coupler moves around on the hitch ball - it sounds like you have a grounding issue. A weak or inconsistent ground connection is often the cause for a whole range of odd lighting behavior on trailers.

It sounds like the ground wire on your trailer harness and/or the ground wire on the Sierra may not be making a clean secure ground connection to the trailer and vehicle frames. This means that the ground may actually be established through the coupler rather than the ground wire as it should. This would explain the on-and-off blinking as the coupler moves about on the hitch ball.

First, check the white ground wire on the trailer to ensure it is secured to a clean bare metal surface on the frame; clean or sand the ground point if it is dirty/corroded and re-secure the ground wire. Repeat the same process on the Sierra.

Next check the condition of the ground contacts on both the male plug on the trailer and the female socket on the vehicle. Even very slight greenish or whitish discoloration can indicate corrosion, enough to interfere with electrical conduction. Clean the contacts with a spray-on contact cleaner (available at most auto and electronics stores) and perhaps a nylon brush like # 814092.

Please refer to the linked article for additional tips.

expert reply by:
Adam R

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