Wiring New Trailer Tail Lights to a Trailer with Only 2 Wires
Updated 05/28/2025 | Published 03/26/2015
Products Featured in This Question
Question:
Need to replace taillights on my trailer. Theres two wires that come out of the trailer for the lights. Only red and black. How do I wire those two wires for my tail lights?
asked by: Gary
Expert Reply:
It sounds like your trailer tail lights you are using now ground through the mounting hardware. That would be why there are only 2 wires. One of those two wires is going to be for turn signal/brake lights and the other is going to be for running lights.
To determine which wire is which you can plug the trailer up to a vehicle and have someone step on the brake pedal while you test the wires at the back of the trailer using a circuit tester such as # PTW2993. Whichever wire lights up the tester with the brake pedal pressed is the turn signal/brake light wire. That would make the other wire the running lights which you can test by turning on the tow vehicle headlights.
On new lights there is usually going to be a yellow wire on the driver side light for left turn/brake lights and a brown for running lights. There may or may not be a ground wire present. If there is a ground wire, usually white, attach it to a bare metal surface on the trailer frame. If there isn't a ground wire, then the light grounds through the mounting hardware.
The same thing goes for the right side of the trailer only instead of a yellow wire for turn signal and brake lights it will be a green wire.
Craig.
5/28/2025
My boat trailer wiring harness for the lights only has 2 wires yellow brown and green black. The lights has 4 wires, how do you wire something like that. Please let me know. Thanks.
Product Page this Question was Asked From
16 Gauge, 4 Conductor Bonded Parallel Wire - Per Foot
- Wiring
- Wire
- Bonded Wire
- 4 Wire
- 16 Gauge
- Deka
more information >
Featured Help Information
Miscellaneous Media
Continue Researching
- Article: Trailer Wiring Diagrams
- Search Results: 1157 replacement bulbs
- Search Results: wire clips and clamps electrical tools
- Search Results: hitch pins and clips
- Shop: Lock N Roll Articulating Coupler with 30" Extension - 2" Receivers - Trailer Side - 11K
- Video: All You Need to Know About the Peterson Trailer Tail Light w/ Steel Housing
- Search Results: ventline screens replacement
- Search Results: replacement crank handle
- Shop: Trailer Wiring
- Shop: Peterson Trailer Tail Light w/ Steel Housing - Stop, Turn, Tail - Incandescent - Red Lens
- Search Results: trailer brakes
- Search Results: battery box lid
- Shop: etrailer Trailer Hitch Pin and Clip for 2" and 2-1/2" Hitches - 3-1/2" Span
- Shop: Brake Controller
- Shop: Dexter Electric Trailer Brakes - 12" - Left/Right Hand Assemblies - 7,000 lbs
- Q&A: Wiring New 3 Wire Light on Trailer to Replace 2 Wire Light
- Shop: Dexter Nev-R-Adjust Electric Trailer Brakes - 12" - Left/Right Hand Assemblies - 7K
- Article: Wiring Trailer Lights with a 4-Way Plug (It's Easier Than You Think)
- Article: How to Tell the Weight Rating of a Trailer Axle
- Article: How to Measure a Trailer Axle
- Shop: Curt 5th Wheel/Gooseneck Custom Wiring Harness w/ 7-Pole Connector and Cover Plate - 7' Long
- Shop: Optronics Single-Face LED Trailer Light - Brake, Tail, Turn - Round - Pedestal Mount - Red
- Q&A: Where Are The Trailer Light Fuses On A 2011 Ford F-250 Lariat
- Q&A: How To Tell Apart 5,200 lb, 6,000 lb and 7,000 Axles
- Q&A: How to Pick Out Bearings for a Dexter P-21 SLR Axle
- Q&A: How to Determine Capacity of Trailer Axle with 8 Lug Wheels
- Q&A: Where do Trailer Wire Colors Green, Yellow, Brown and Red Run To
- Q&A: What Color Trailer Wires go to the Red, Black and White Taillight Wires
- Video: Complete Breakdown of the etrailer Trailer Wiring Junction Box
- Video: Complete Breakdown of the Brake Mounting Flange for 3" Round Axle
on Wiring
Robert M.
9/8/2024
Installing a set of optronics led lights on my small boat trailer,and I only have two wires on both lights yellow &brown, green brown,& no white wire.how do I ground the lights? Please!!il I would be grateful any information
Jesse M.
9/9/2024
Jason B.
10/14/2024
Jesse M.
10/15/2024