Troubleshooting 7-Way Trailer Wiring Where Colors Arent a Match

Question:

I have a double axle dump trailer and can’t get the wiring right to connect a 7 way adaptor to the truck. Trailer wires are red, white, black, green, yellow, green-brown and yellow-brown

asked by: Matt R

Expert Reply:

For your trailer connections I recommend the 7-Way Molded Trailer Plug with Junction Box # HS381-9000 along with ring terminals # 44-5310A. To match the functions, I can't tell you what the colors your trailer wiring are, so you will either need to trace the wire colors to find the location or you can use a battery and a jump wire to test each color wire for function. I've attached an article to help with trailer wiring to assist.

You will have 7 functions represented, but the colors you stated would lead me to try the following first as it is likely based on the color information you sent:

Green is normally right turn and brake light
Yellow is normally left turn and brake light
Brown is normally running light, so brown yellow will most likely be left side and brown green the right.
Then you have white which is normally ground,
The black is normally 12V power
The red is where is gets more difficult. Normally the trailer brakes are blue so this is where you know there has been some color change so you want to check for function. If the red wire splits to each side and goes to your brake assemblies, then you have confirmed based on location.