How To Power Running Light Circuit Of Trailer With 4 Way Flat Pulled By Tractor With One Light Wire
Updated 03/18/2026 | Published 03/16/2026
Question:
I would like to be able to connect my trailer lights to my tractor. My trailer is wired with the flat 4 connecter, but my tractor only has one wire run to the rear for the rear lights. Is there a way that I can use that wire to connect it to my trailer to use the main trailer lights? I realize that the turning signals and brake lights would not work.
asked by: Mervin
Expert Reply:
Hey there Mervin, there is definitely a way to power your trailer running lights by your tractor's single power wire for lights.
I'd grab something like TowSmart Trailer Connector - 4-Wire Flat Set # TS46RR (or find something locally if need be). You likely won't need the trailer 4 way end, but just use the 48" long harness with the female 4 way flat for the vehicle side. Just hardwire the tractor's single light wire to the brown wire on the vehicle end harness, then plug into your trailer's male 4 way flat conneciton.
This will power the trailer's running light circuit only. Hope this helps! Let me know if you need anything else.
Do you run the tractor and trailer at night often?
(click to enlarge)
Product Page this Question was Asked From
TowSmart Trailer Connector - 4-Wire Flat Set - 12" Trailer - 48" Vehicle
- Trailer Wiring
- Trailer Connectors
- Trailer and Vehicle End Connector
- 4 Flat
- Plug and Lead
- TowSmart
more information >
Continue Researching
- Video: Curt T-Connector Vehicle Wiring Harness Installation - 2019 Honda Accord
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Video: Curt T-Connector Vehicle Wiring Harness Installation - 2021 Mazda CX-5
- Video: Curt Custom Fit Vehicle Wiring - Trailer Hitch Wiring - C56377 Review
- Shop: Towing Kit w/ Ball Mount and Trailer Wiring for Stealth Hitches Hidden Rack Receiver - 2" Ball
- Shop: Peterson Combination Trailer Tail Light - 7 Function - Incandescent - Square - Driver Side
- Search Results: trailer hitch
- Shop: Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector
- Article: Trailer Wiring Diagrams
- Video: How to Choose a Trailer Brake Controller
- Q&A: What is the Difference Between a Class II and a Class III Hitch?
- Search Results: trailer wiring
- Q&A: Lug Nut Torque Chart for Trailer Wheels
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- Video: Curt T-Connector Vehicle Wiring Harness Review C56040
- Shop: Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires
- Video: The Low-Down on the Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Search Results: trailer tires and wheels
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Q&A: What is the Difference Between a 4-Way and 7-Way Trailer Connector
- Video: Clean Up Your Trailer Wiring
- Q&A: Installation Time for Blue Ox BX1128 Flat Tow Base Plate Kit for 2016 Jeep Grand Cherokee
- Search Results: trailer jack
- Article: How to Measure for Trailer Hitch Drop
- Q&A: Recommended Bike Rack and Dual Hitch Adapter for Carrying E-Bikes While Flat Towing
- Search Results: trailer lights
- Article: How to Measure Your Trailer Wheel Bolt Pattern
- Article: How to Choose the Right Trailer Hitch Class
on Custom Fit Vehicle Wiring
Mervin
3/18/2026
Thanks! No, I don't run it a lot after dark. I also use a battery-operated magnetic flashing light but thought it would also help to have my tail & running lights.