Troubleshooting 7-Way Wiring Missing a Wire on Random Axle Trailer With Brakes.

Updated 12/27/2021 | Published 12/26/2021

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Question:

Wiring for random axle trailer with brakes on trailer. I have white black yellow green brown red. Basically white ground Black ? Red auxiliary Yellow left turn Green right turn Brown trailer lights All charts show a blue and a purple. But I have neither there is No purple or blue wire on my trailer. Please help

asked by: Bart W

Expert Reply:

7-way wiring colors can vary on a trailer. The # HM11141144 from your question follows the traditional SAE (See the diagram below) with red for the 12V power instead of black. The purple in this case would be the reverse lights. On the RV standard it would be yellow instead of purple. The only way for you to be sure which wires are which is to trace them back to see where they go.

With both a red and black wire, more than likely the black is 12V power and the red is the left turn/stop. Again, the only way to be sure is to see what they are attached to. One thing is for certain, you are missing a wire. The blue wire is the brake controller output. This will be necessary for your brake controller to activate your brakes. If you need to add this wire I recommend using the 10 Gauge Primary Wire - Blue - per Foot # 10-1-1

I have attached some helpful articles on trailer wiring for your reference.

expert reply by: Robin H