WIRE WE HERE?
Rewiring his 1958 James Captain and having read conflicting advice elsewhere, Andrew Gavin asks what gauge wire he should be using. Well, although thick wire has less resistance than thin, making it a more important issue at six volts than 12, I’d guess any decent automotive cable would do.
The James’ lights probably use about 30 watts, which at six volts is five amps. Ferret explained that the old 1mm squared cable was rated at 8.75 amps and the heavier 2mm cable 17.5 amps. Despite being apparently thinner, modern thin-wall cable is actually rated higher – 16.5 amps for 1mm and 25 amps for 2mm. So while any of these would be adequate, if Andrew uses thin-wall 1mm for the lighting circuit and 2mm for the battery, ammeter (if fitted) and main earth leads, he will have a bulletproof system. But he stressed the importance of using quality connectors, properly fitted and making sure the earths are good.
Something I’ve noticed is that pattern parts – like tail-lights – often come with poor quality wire; the insulation is thick, but there’s barely any copper in the middle. There’s not much point connecting that to your quality harness.