Troubleshooting Right Side Brake and Turn Signal Not Working With Running Lights On

Question:

Hi, have a fifth wheel with a tail light not working properly on one side. With the running lights on, the right tail light, brake, turn signal won’t work. With running lights off, the brake and turn signal work but dimmer than the left side.

asked by: Jim G

Expert Reply:

The first thing I would do is check the 7-way connection on your truck. Make sure there is no debris or corrosion present and clean as necessary. It wouldn't hurt to go ahead and check out the connector on the trailer as well. Once this is done, go ahead and test the functions using a circuit tester like the # PTW2993. If you aren't getting power with the running lights on then you know it is on the vehicle side. If everything checks out it is a problem with the trailer wiring.

In both cases I would check the ground connection which is likely the issue. You can inspect the ground wire for a short and ensure that the connection is secure on a clean, bare-metal surface. If the ground is fine I would look for a short in the wiring for your right brake/turn signal and repair as needed.

expert reply by: Robin H