Causes of copper wire blackening in rubber sheathed cables
If it is copper aluminum wire, it is better to change, because the copper plating has been completely oxidized, lost utility. If it's a copper wire and the skin is not bad, you don't have to change it.
Copper is generally black had been struck by lightning or large current caused by the first to confirm this line is the copper wire or copper wire, now there are a lot of copper as copper wire, this line can not withstand the power load, and easy oxidation black coating
The use of time is too long, there may be copper wire diameter is too small, general wire will be, is a long time the reason for aging, as long as the use of time without heat can be used.
