The Guild of Automotive Restorers The old electrical harness in your car, if the car is mid fifties or older, is cloth wrapped copper or aluminium wire, usually with an inner sleeve made of a rubber or rubber like compound. These harnesses served well in their day but as they aged they became brittle. Dampness, heat and age rot the cloth and the inner insulator becomes hard, brittle and inflexible. The wire outer casing cracks and after a while small sections will actually fall off, leaving a bare wire hanging under the dash or running through your interior, engine compartment or chassis.

The Guild of Automotive Restorers If that wire comes into contact with metal or another wire you will have a dead short. In more modern cars with twelve volt systems a dead short in the harness will usually result in a popped fuse. The old six volt systems don't give the safety of fuses. If you have a dead short, heat builds up, often throughout a major part of your harness. This heat becomes so intense so quickly that the insulation starts to smoulder and will catch fire within seconds of the short occurring.

The Guild of Automotive RestorersIt is best to remove old and abused wiring harnesses and replace them with a new harness. If you are worried about the originality of the appearance of your wiring, you can get a brand new harness made for any car in the original cloth bound wiring. The only change to these wires is that the internal insulator is made from newer and much improved materials.