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Why the Different Color Systems for 4-Way and 7-Way Trailer Connections?


Seven wire color codes vs four wire color codes. When I connected a new seven connector harness to my trailer, I matched the wires color for color. The left turn signal flashed the running lights, the headlights turned on the right turn signal and the right turn flashed the right running light. When I compared the color chart associated with my seven connector harness to a chart for a four wire harness I noticed the color codes were completely different except for white, it was ground for both. My trailer appears to be wired according to the four wire code so it should be a simple fix for me to switch a few wires. My question is why the different color systems?


Helpful Expert Reply:

That is a really good question, and unfortunately the manufacturers don't give a direct answer. They just say matching function is what is needed and colors don't always match from any vehicle or trailer manufacturer.

I have found color coding makes a whole lot of sense with the traditional color functions being brown for running lights, yellow for left brake/turn, green for right brake/turn, white for ground. This has been the industry standard for trailer lighting on smaller trailers for decades. Then for 7-way you add the blue for brake controller, black for 12V power, and purple for reverse light on traditional color systems.

Some manufacturers follow this and others like Hopkins give a completely different color code for what seems to be no reason other than already addressed above. I've attached the chart for the Hopkins 7-Way RV Style Connector with Molded Cable - Trailer End - 8' Long - RV Standard # H20046 as an example.

If you don't have the conversion chart it gets even more fun to match functions with locations. I've attached an article to further assist.

click to enlarge
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