I bought a third brake light from a 1992 325ic (convertible) that goes on ther rear trunk lid. I will be using this light on an old classic car.

My question is, there are 4 wires leading to the brake light:

Brown
Green/Red
Green/Black
Green/Black

The only two that I see that work the light are the brown & green/red. I tried several combinations and only the brown & green/red work the light.

What are the other two Green/Black wires for?

Thanks,

Dave