Chances are real good that the wire colors in your trailer won't match the colors on a modern 7 pin connector.
Typically the wire colors are:
Red= Left Turn
Brown= Right Turn
Backup= ??? Could be black, but a small gage wire
The remaining 2 wires are:
The charge line and the actual brake wires. Typically these are larger gage wires. #10
If you use a battery charger. You can ID each of the circuits by connecting the black lead on the charger to a clean spot on the chassis. Then use the red lead and touch each of the wires on the UCord and note what it is.
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