4-Way Trailer Connector that has 5 Wires

Updated 02/29/2024 | Published 05/01/2015

Question:

The dog chewed up the flat connector on my trailer which has five wires, white, green, yellow, brown, and black. I bought a four wire flat connector at Autozone, for the trailer, but only offers a four wire connection. Do you run two of the five wires into one connection position, and if so, which ones? Or, does the black wire even need to be connected?

asked by: David F

Helpful Expert Reply:

Did you have a 4-pin connector that had 5 wires or was it a 5-pin connector? There is a big difference since you normally see a 5-pin connector on a boat trailer with the 5th pin used for an electric reverse lockout solenoid on a brake actuating coupler. If it was a 4-pin connector with 5 wires then it is called a wishbone harness and would have 2 wires attached to the running light pin so you have one wire for each side of the trailer.

Typically, on a 4-Way, the white wire is ground, brown is running lights, yellow is left turn/brake lights, and green is right turn and brake lights. A 5-Way will have the same functions but then usually a blue wire at the end for that electric reverse lockout I mentioned.

On a wishbone 4-Way you would have a ground wire and then you usually see a brown wire with yellow stripe for the left side running lights and a brown wire with green stripe for the right side running lights. They are attached to the same pin. All of the other functions are the same.

expert reply by: Michael H

Marshall

2/29/2020

Well from the original question, what do you attach the black wire to?

Chris R.

3/2/2020

This depends on if it's a 5-way connector or actually a 4-Way connector with 5 wires. Just going by the process of elimination, if it's a 4-Way the black wire would be one of the running lights circuits along with the brown. If it's a 5-Way I have to assume it would be the reverse circuit wire. If you can tell which pin/terminal on the connector the wire's actually leading to, I could hopefully give you a more certain answer.

Dennis B.

2/25/2024

@ChrisR I have 4 pin 5 wire Trailer brake has a black and white. Where does the black tie into?

Mike L.

2/27/2024

@DennisB A 4-pin connector won't have the provision for trailer brakes. What braking system does your trailer use? Electric, or do you have a surge coupler that compresses when the tow vehicle brakes which hydraulically actuates the brakes?

See All (6) Replies to Marshall ∨

Mark C.

5/10/2020

I have a 5 wire to 4 flat , I put the green to green, yellow to yellow and the 2 brown with stripes to the the running light pin and white to white, I have no brake lights and no right turn?

Chris R.

5/13/2020

From where I'm sitting you seemed to have wired everything up correctly (unless your trailer uses odd wire colors). I might take a circuit tester to the 4-Way on your tow vehicle just to make sure you're even getting appropriate power there - the issue might be on that side. Test the pins while you have each light function activated to ensure you're getting power from the vehicle - if not, check for blown or missing fuses under the hood, frayed wiring on the harness, etc. If the vehicle checks out, make sure the light assemblies are still securely grounded and inspect any wiring you can access for damage. Let me know what you find and we'll keep going if needed!

Dennis A.

11/16/2021

I have a 4pin flat hooked to a wishbone 5 wire flat. Dim running lights . Could it be that the trailer is grounded through the ball when hooked up . Could that be a double ground?

Les D.

11/23/2021

Behind the bumper, the truck has a white wire coming off the back of the connector receptacle. That white wire grounds to the truck nearby the truck receptacle. The white wire that goes to the trailer also connects to a conductive part of the trailer. The trailer could ground through the ball, but it is more reliably done through the ground wires. Remove the screws grounding to the truck and trailer. file the connection point to shiny metal, and file the connector ring clean as well. Poor grounding is most likely the cause of your dim lights. If you happen to have a second truck around you could hook up the trailer to determine if the problem is on the truck side or trailer side. Let us know if you need further troubleshooting.