How To Wire License Plate Light/Bracket With 3 Wire Connection

Question:

Connecting bracket license plate light with yellow black and red wires. What do I connect to on a 4 pin connector. Also if I dont use all 4 wires on 4 pin do I just cut it off?

asked by: Frank

License Plate Brake With Light and 3 Wire Connection
(click to enlarge)

Expert Reply:

Most Trailer License Plate Lights with a Bracket like the Optronics # LPL55CB you found are only going to have 2 wires a power and ground for the light. It looks like yours has either an additional light for either a reverse light or brake light. While I cannot tell who manufactured your light you are most likely going to have to test the light with a 12 volt battery to determine which wires are power and for which function and which is the ground. Typically white or black are the most common ground wires so that is going to be the best place for you to start your test. On a 4-Way # HM38138 the white will be for the ground and brown for the running light for the license plate. The yellow is for the left turn signal/brake light and the green is for the right turn signal/brake light.

expert reply by: Bud M

Frank

4/25/2024

One ground and ones running light. The yellow is for brake light . So my question is to spliceonto a 4 pin should I connect yellow, a three way splice between the turn signal wires and the yellow on plate lite.

Bud M.

4/25/2024

@Frank To use the additional light only as a brake light you would need the Module # PP20-702. This will connect to both the yellow and green wires on the 4-way. It detects when power is seen on both circuits to then send power down its green wire for the brake light. So you would connect the yellow wire on your light to the green wire on the module. The 2 yellow wires on the module will connect individually to the 4-way's yellow and green wires.