Car wires are carried tightly bound in the loom. In order that you can, with the aid of a wiring diagram, trace which wires go where, the wires are colour coded. Many elderly cars have at some time been fitted with extra lengths of wire, either to replace damaged lengths or to power an extra device. Sometimes, the wires are of an appropriate colour and rating, but often they are not.
A damaged loom (frequently caused by welding too Close to the loom and melting off the insulation, often caused by shorting to earth which also burns off the insulation) is best replaced — even though looms are far from cheap to buy and anything but easy to install. Damaged individual lengths of wire outside the loom may be replaced with others of the same colour and diameter, except in cases where the damage is melted insulation and the wire runs into the loom, because the wire (and adjacent wires) in the loom could also have melted insulation.
Wire damage includes anything which bares the copper core or anything which reduces its effective internal cross sectional area, such as being pinched so that some of the strands of wire break but others survive. Check all visible wiring in the car for damage, and also check that spade and bullet connectors are insulated — it is not unknown for an un-insulated connector to drop off its terminal and start a fire.
A damaged loom (frequently caused by welding too Close to the loom and melting off the insulation, often caused by shorting to earth which also burns off the insulation) is best replaced — even though looms are far from cheap to buy and anything but easy to install. Damaged individual lengths of wire outside the loom may be replaced with others of the same colour and diameter, except in cases where the damage is melted insulation and the wire runs into the loom, because the wire (and adjacent wires) in the loom could also have melted insulation.
Wire damage includes anything which bares the copper core or anything which reduces its effective internal cross sectional area, such as being pinched so that some of the strands of wire break but others survive. Check all visible wiring in the car for damage, and also check that spade and bullet connectors are insulated — it is not unknown for an un-insulated connector to drop off its terminal and start a fire.