After Installing New Trailer Lights and Wiring, Trailer Lights Will Not Work Properly

Question:

I installed new lights and wire on a trailer.I hooked them up as directions stated and the tail lights worked but the blinkers were both flashing when i turn either turn signal on.When i hit the brakes it would cut off all lights.I reversed the wires at the light assembly on the trailer.Now the tail lights work,turn signals work properly but the brake lights dont work at all.If the tail lights are on it shuts them off when i press the brake..Please help.

asked by: Jeff T

Expert Reply:

This sounds like a ground problem and possibly a wiring issue. The lights should have something that indicates the wire functions on the back of the housing so it is easy to check those. There should be one wire for the turn signal/brake lights, and one wire for running lights. Then there will be either a separate ground wire or the lights ground through the mounting studs.

When there is a weak ground not all functions will work. A weak or bad ground can be caused by corrosion at the grounding location. Also you will want to make sure the main trailer connector ground is attached to a clean and corrosion free bare metal surface.

Aluminum trailer frames, tilt beds, and folding tongues can also cause ground problems. Running jumper wires from the light grounds to the main trailer connector ground can help.

Ground issues usually show up when there is more load drawing power. The constant draw of running lights or the brighter brake lights do create more draw.

If you are using an adapter such as # 37385 that you referenced the adapter could be faulty. I have included some links that explain the common pin outs for trailer connectors and troubleshooting vehicle side connectors.

expert reply by: Michael H