Trailer Wiring Has 5-Wires White, Yellow, Green, and 2 Browns

Question:

I have attempted to repair a 4 wire connector on my trailer. When repairing I have a white wire/ 2 BROWN wires, yellow wire and Green. I can only get the tail lights to come on. NO turns, brakes, etc. What should I do with the 2 brown wires. On the old connector it looks like the 2 BROWNS went into the connector together. Any advice would be appreciated

asked by: Dexter K

Helpful Expert Reply:

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. 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: Chris O

Joe

1/27/2025

Trailer wiring….white, yellow/brown wire, green/brown wire. Vehicle wiring… white wire, yellow wire, green wire, black wire

Bryce D.

1/27/2025

@Joe Hey Joe, what exactly did you need help with? I'm assuming you're wanting to know what wires go to what so on your trailer side: The yellow/brown is going to go to your yellow on your vehicle side, the white goes to the white, the green/brown goes to your green, and the black is your 12v power. Let me know if there is anything else I can help you with!

My G.

2/28/2025

My trailer 4 prong wiring is old. It has a a green wire and a green wire w brown, a lone white, and white and white brown

Kate F.

2/28/2025

@MyG Hello My G (digging the chosen the name), I ran into this issue with I rewired my boat trailer, the person before me had all kinds of different wire connected, it was a mess. The best way to figure out what color wire does what function is to either trace the wire back to see what it is connected to, or to use something like a Hook Probe Circuit Tester # PTW2993 so that you can test the wire to the function by connecting the trailer to the vehicle turning on your right blinker, then test the wires to see which one it is, then other blinker, and apply brakes. There is not a true color code when it comes to trailer wiring, so you always want to match the function, not the color wire. What kind of trailer are you working on?

Tom

3/9/2025

I have a wishbone harness on my 2002 carry-on trailer. The squirrels ate my wires on the plug side. Replacing it with a four wire plug. I wired everything up, White to white, green to green, Brown wire to brown and yellow and brown wire to brown and green wire. . I have brake lights I have directionals, but no tail lights. Is that normal? Could it be the bulb? And I’m not sure what bulbs are in there. Please advise. Thank you.

Kate F.

3/10/2025

@Tom Hey there Tom. Sounds like you have things wired up correctly. Did you try the running lights (tail lights) with your headlights on? I have heard on some vehicles hooked up to trailers that the headlights need to be on for the running lights to work, worth a try. I would also double check the ground to make sure it has a good clean connection, all kinds of crazy things can happen with a bad ground. Lastly, check the power going into the 4 way and coming out with something like a Hook Probe Circuit Tester # PTW2993. Please let me know what you find out. Those pesky squirrels might have eaten through more of the wires.

Tom

3/10/2025

@KateF I called my local trailer guy this a.m. He’s done work for me on this trailer and i bought an additional trailer from him. He told me to check the fuse box under the hood. Some trucks have fuses for the trailer. I went in and checked it out and B-I-N-G-O little mini 20 amp fuse was blown. Went to advanced auto parts. Got a pack of 20 amp fuses and voilà. Fixed. I guess we learn something every day. Be well, and thank you. I hope this information assist you and others. TG