Old Trailer Lights had 3 Wires and New Trailer Lights have 2 Wires

Updated 09/13/2016 | Published 09/12/2016

Question:

Hi, Old lights were Peterson 440-15s using 3 wires to power e.g. 2 yellows and 1 brown for drivers side tail light. New lights are Blazer Intl from light kit C6423 incandescent that only have 2 wires coming from the light: e.g. 1 yellow and 1 brown on drivers side. Do I just splice the original 2 yellows together and join then to the single new yellow green to green on passenger side of course? The brown to brown is not an issue as amber market lights already done. Thanks for any help,

asked by: Ted A

Expert Reply:

Usually when a light has 3 wires one of them is a ground, one is running lights, and one is brake/turn signals. And usually on a light with 2 wires it will ground through the mounting hardware and one wire will be for running lights and the other for brake/turn signal.

I am not sure how your old lights were set up or why it would have 2 wires that are the same color unless the trailer had separate amber turn signals. This is uncommon on trailers in North America though because they brake lights and turn signals operate on the same circuit.

To determine which wires to attach to your new lights we need to know what each of the wires does. The new light-yellow wire is for brake and turn signal and the brown is for running lights. Attach the appropriate wires on the trailer to match these functions.

To determine the functions, you can plug the trailer into the vehicle and have someone go through the light functions while you test the wires with a circuit tester such as # PTW2993. Then you can splice in the light wires accordingly.

expert reply by: Michael H