Wiring a Replacement Submersible Trailer Tail Light  

Question:

Expert Reply:

The Optronics Submersible Trailer Tail Light, part # ST16RB, that you purchased will have 3 wires coming out of the back. There will be a white wire for ground, a brown wire for tail light function and a green wire for the right turn and brake function. There is not a molded plug available for this light and you will first want to determine the function of the two wires coming from the plug from the old light.

There are two options, the two wires may be a ground wire and a right turn signal lead, or if the light grounds through the hardware the functions of the two wires may be for the turn signal and the tail light function. Most likely your light grounds through the mounting hardware and the two wires are for the turn and tail light functions, but I have included additional details if this is not the case.

If the light grounds through the mounting hardware and the two wires from the plug are for the turn and tail light functions, then you can simply cut off the plug and connect the wires from the light to the wires from the trailer according to their function. Brown will connect to brown and green will connect to green. This light does not ground through the mounting hardware so you will want to ground the white wire on the light to the trailer frame.

If one of the wires from the molded plug are a white ground wire, then the other wire on the plug will probably be for the tail light function. This is usually only the case for tail light markers that do not use the turn signal function. You can simply remove the ground wire from the plug and cut off the other wire as close as possible to the plug in case you need the extra wire. If you are using this light as a tail light and turn signal light, you will need to locate the right turn circuit coming from the trailer connector near the tongue and connect that wire to the green wire coming from the light.

Waterproofing these connections is fairly easy, you can connect the wires using butt connectors like part # 05730-5 and sealing that connection with either liquid electrical tape like part # SWC50122 or heat shrink tubing. We do not carry heat shrink tubing, but it can be found at most automotive and hardware stores. I have included a video that demonstrates the replacement of a tail light on a trailer, but it is on the left side of the trailer and it is of a similar, but different tail light.

expert reply by: John H

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