Replacing a 4-Way Trailer Connector that has 5 Wires with a 4-Way that has 4 Wires
Updated 08/15/2026 | Published 04/07/2019
Question:
Ive got 5 wires going into a 4 flat......trying to put a new 4 flat connector on my trailer and it only has 4 wires.....whats the extra wire and what do i do with it??
asked by: Richard
Expert Reply:
So you're removing a 4-way that's currently on your trailer that has 5 wires and replacing it with one that only has 4 wires? It would be easier to replace it with one that has 5 wires, like part # A35W42B, but if you've already got a 4-wire connector you can still install it.
The 5-wire connector is called wishbone and it has a second running light wire so you can run one of them down each side of the trailer. It keeps you from needing to use a jumper to go from one side to the other so the install is a little easier. Since your trailer is already wired this way you can connect the two running light wires together and then connect them both to the running light circuit on the new 4-way. Traditionally this is the brown wire and it connects to the pin closest to the ground pin. The ground pin is the one that's female.
Product Page this Question was Asked From
35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground
- Trailer Wiring
- Trailer Connectors
- Trailer End Connector
- 4 Flat
- Plug and Lead
- Optronics
more information >
Featured Help Information
Miscellaneous Media
Continue Researching
- Q&A: Wiring New 4-Way Connector on Trailer with 5 Wires
- Shop: 35 Ft 4-Way Trailer Wiring Harness - Wishbone Style - 42" Ground
- Search Results: wesbar trailer wiring
- Q&A: Connecting 5 Wires From a Trailer to a 7-Way Trailer Connector
- Q&A: Why Does 4-Pin Trailer Wiring Have 5 Wires
- Shop: Trailer Wiring
- Q&A: 4-Way Trailer Connector that has 5 Wires
- Article: Trailer Wiring Diagrams
- Search Results: trailer hitch
- Q&A: What is the Difference Between a Class II and a Class III Hitch?
- Shop: Curt Powered Tail Light Converter with 4-Pole Flat Trailer Connector
- Shop: Trailer Hitch
- Search Results: trailer wiring
- Q&A: What is the Difference Between a 4-Way and 7-Way Trailer Connector
- Video: How to Choose a Trailer Brake Controller
- Article: Brake Controller 7- and 4-Way Installation Kit (ETBC7)
- 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
- Search Results: trailer tires and wheels
- Article: How to Measure for Trailer Hitch Drop
- Shop: Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Shop: Suspension Enhancement
- Q&A: Installation Time for Blue Ox BX1128 Flat Tow Base Plate Kit for 2016 Jeep Grand Cherokee
- Search Results: trailer jack
- Shop: etrailer Trailer Hitch Receiver - Custom Fit - Matte Black Finish - Class III - 2"
- Video: Curt T-Connector Vehicle Wiring Harness Review C56040
- Article: Wiring Trailer Lights with a 7-Way Plug (It's Easier Than You Think)
- Shop: Brake Controller
- Shop: Gooseneck Hitch
- Video: Curt Powered Tail Light Converter Installation - 2023 Kia Telluride
on Trailer Wiring
Michelle
8/15/2026
So I cant use a 4 if it requires a 5..cause I cant seem to get it wrk like when the I press the brake the lights dont turn on