Trailer marker light issue

It's usually the center pin on a regular pigtail.

 

The only difference between the color coded green and yellow is the plug pins. The green is traditional round studs and the yellow is the new iso oblong studs. The wire colors and functions within the cord are the same. Green was adopted to allow drivers to know the tractor was equipped with the abs controller for the trailers back before the trailers were built with their own on board controller. Other then the pin difference the color doesn’t matter with the new equipment in the last 15 years. Black cords will do the same thing as green.

 

Yes. Center Blue wire pin for abs was was adopted in the industry on all cords. Before that time on majority of rigs the Blue was either an unused dead spare. In some cases it was used as an auxiliary for something added on.

 

you need a 12 ga wire for the abs not 14, which was what the green was for over black

 

True. The greens are standard 8/10 / 12ga. But they have made 1-8ga 2-10ga / 4-12ga standard black for 40 years. Just no one wanted or wants to pay the higher cost and always boughtthe cheaper 10 / 12 / 14 cords. So making them use green in this day and age solved that. I think the cord on my ‘67 is date coded for ‘93 and its the big one. Had the center blue pin wired to a toggle switch to power abs trailers if needed. Now I have it wired into an electric brake controller as well for RV style plug and utility trailer with electric brakes. Works for both.