Which Wires Should be Tapped Into When Adding Additional LED Marker Lights on a Boat Trailer

Updated 09/18/2024 | Published 02/08/2011

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Optronics Streamline LED Trailer Tail Light - Submersible - 3 Function - 11 Diodes - Red Lens

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Hook Probe Circuit Tester

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Question:

My trailer is fully wired with LEFT and RIGHT SIDE MARKERS and BRAKES/TURN SIGNALS already. I am wanting to run some additional White LEDs that shine up on the boat for looks when Im driving at night. How can i do this properly without having an auxiliary wire coming from my wiring harness? I tried splicing the side marker wire but I did not get any power that way. Thanks

asked by: Micah M

Expert Reply:

In order to add LED lights that shine on your boat at night, they will need to be wired into the running light wire or wires on the trailer. On a typical 4-Way flat, it is the brown wire coming from the trailer side connector. To be certain, you can use a circuit tester like # PTW2993.

With the trailer connector and vehicle lights on, probe the wires coming from the back of the connector until you find the one that is hot all the time. You can trace this wire back to where you want to install the new lights and tap into them there.

A word of caution, adding extra lights may be too much of a power draw on the wiring system causing some or all of the lights to not function properly or it could even cause damage to the wiring on the trailer or vehicle. The remedy for this is to use a powered converter on the towing vehicle which will get the power for the lights from the vehicle battery. Also, you will want to make sure that the lights are properly grounded in order to complete the circuit so the lights will work.

expert reply by: Michael H

Scott

9/17/2024

I added additional led marker lights to my trailer. The new lights have a yellow and black lead. I ran the wires to my junction on the trailer. I attached the yellow wire to the brown wire and connected the black wire to the white wire on the trailer. When I connected the truck to trailer none of the marker light new or existing worked, plus it blew the trailer running light on my truck. How do I make this work??

Jameson C.

9/17/2024

@Scott It sounds like you ran power to the ground wire or otherwise miswired the lights. You really need to determine the functions of the wires. If the lights are dual function (have a low and high intensity) they actually would ground through the mounting hardware.

Scott

9/17/2024

@JamesonC they are single function high intensity, the fuse that blew was a 20amp when the trailer was connected to the truck. When I took one light and attached it to the trailer junction box yellow to brown wire and black wire to white it worked. So I then added 5 more by soldering them together and making one harness again connecting the yellow to the brown wire and the black wire to the white wire. Once I connected the trailer to the truck it blew the trucks 20 amp fuse. I then just decided to remove the connections from the junction box and I the hooked them to jump box and they all worked fine. As soon as I reconnect them to the trailer junction box they all blow the fuse out again.