Troubleshooting Trailer Wiring that Blinkers Dont Work When Headlights are On 2007 Toyota 4Runner

Question:

Hi, I have a 2007 Toyota 4 Runner with 7 prong connector to 4 way wire. I just wired up the trailer today. -Adapter 7 Pole to 4 Pole with Tester and Cover - 47345 -35 ft. Wishbone 4-Way Trailer Wiring Harness with 42inch Ground Wire - A35W42B It only has 4x total wires: passenger side green - brown driver side yellow - brown I used butt connectors at the lights. When I have the truck lights off, both blinkers work fine. When I have the truck lights on, both lights are illuminated, however, the left blinker works, but the right does not. The brake lights work in both situations I believe. I would think connector, but the blinker works with the lights off, running lights work and brake lights work. Am I missing something here?

asked by: Steve

Helpful Expert Reply:

This sounds like a ground issue. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light. Make sure that the vehicle side and trailer side connectors are clean and free of corrosion inside and out. The main connector grounds should be attached to clean and corrosion free bare metal surfaces.

The light grounds should also be attached to clean and corrosion free bare metal surfaces. If there is anything between a light ground and the metal trailer frame or if the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the light grounds to the main trailer connector ground can help.

I attached a link to an FAQ on trailer wiring for you to check out as well.

expert reply by: Jameson C