I'm currently working on my trailer, re-flooring and rewiring it. I stopped
by NAPA a while back and bought a set of two matching connectors.

I put one on the car side like this:

Car side new connector
White
Brown
Yellow
Green

Today I set out to replace the trailer side connector with the new one. I
discovered that the new connector has four wires, like this:
White (ground)
Brown
Yellow
Green

just like the new connector I put on the car (which has a euro conversion
brick kind of thing spliced into the tail light wires).

However, the trailer, which has the Harbor Freight wiring, light and
connector set it came with has a fifth wire, like this:
White (ground)
Brown with yellow stripe
Brown with green stripe
Yellow
Green

Can anyone tell me what is going on, and what to do about this?

Thanks,

Jim