Troubleshooting Trailer 4-Way Harness Where Only Running Lights Work

Question:

I have 2011 ford f150no tow package with both the 7 and 4 way harness. I just bought a used utility trailer made by tractor supply. I have running lights on the trailer but both brake lights and both turn signals do not work. I borrowed a trailer from a friend 2 weeks ago and everything seemed to work. I used the 7 point harness that time. I just quickly tested both harnesses and it seems like the only thing that lights up the pen tester is when I touch the ground tab in the harness. What am I missing.

asked by: Neal

Expert Reply:

Sounds like you may have some blown trailer wiring fuses under the hood of your 2011 Ford F-150 and that is why the stop/turn signals aren't working yet the running lights are. That would be the first thing I would check.

Next I would check the trailer connector for corrosion and clean as needed.

I attached a help article on troubleshooting 4-way installs for you to check out as well.

expert reply by: Jameson C