Troubleshooting Turn/Brake Signals on Trailer with New 4-Way and 5 Wires

Question:

4 pin trailer connector. I have 5 wires on trailer harness.gr. wh. yel. and 2 solid brown. I have tried the wire connection of gr-gr wh-wh yel-yel and both Browns to brown. Only have lights. No brake or signals. Do I need to connect an individual brown to the green and yellow.

asked by: Jerry C

Expert Reply:

It sounds like your trailer has a wishbone wiring setup that uses a separate running lights circuit wire (brown) on each side of the trailer. In terms of standard trailer wiring colors it appears that you have wired the new 4-Way correctly, the issue might be that your trailer simply doesn't use standard wire colors for its lights.

This can happen on older trailers that have maybe had a couple owners or even new ones that were the victim of some "creative" wiring at the factory. Determining wire functions by color on a trailer is a good starting point, but it's not always accurate so it's always best to actually test them to verify what circuit each carries.

You can apply 12V power to each of the wires you mentioned to see which light assemblies they activate.

It's also a good idea to inspect any wiring you can easily access to make sure it's in good condition. Also check the light assemblies themselves to make sure they are properly grounded to a clean, bare piece of metal.

If you let me know what you find we can go from there and continue the troubleshooting process!

expert reply by: Chris R