wire

[les]

In the course of rewiring, I needed to lengthen some wires, so I cut one back to solder a bullit connector on, and found that the copper wire was black inside the plastic insulation, so I went further back to find the same. It cleans up ok, back to copper, but wondered why this was/is? It is the lighting circuit, could it have overheated at some point?

[bigginger]

I don't know, but it seems to be true of all old Minor looms
a

[aupickup]

it is called black wire

we used to get it on the wires in our radio controlled aeroplanes

[MoggyTech]

This is caused by dampness at the end of the wire. The copper goes green, then dye from the insulation leeches into the copper and it goes black. This then migrates along most of the wire. It's called 'Black Wire' strangely enough.

It tends to make the copper brittle, so replaceing the effected wires is reccommended.

[les]

Thanks for the information, not heard of that before.