Troubleshooting Trailer Taillight that Stops Functioning When Brakes are Applied

Question:

when I press the brake in my van my left hand parking light goes out why

asked by: Tony

Expert Reply:

Try improving the grounds of the trailer's wiring and you'll see the problem go away. What you described is a classic insufficient ground scenario. The brake lights draw the most current of all the trailer lighting functions so when you hit the brakes if a weak ground is present it will shut the circuit down.

Check first that the light assembly has a good ground. It may ground through the mounting hardware so you might have to clean where it attaches to the trailer. You can also check to make sure the main ground of the trailer wiring (the wire that runs from the connector to the frame is connected properly.

expert reply by: Jameson C