Text b conductor materials

The conductor material used in car wiring is generally copper, although some copper-clad aluminum cable is available. Copper is used for its durability and low electrical resistance.

Conductors come in several strand configurations for various uses. Because of its relatively large cross-section, single strand wire is least desirable where flexing is likely to occur, so it is rarely, if ever, used for automotive wiring.

Multiple-strand wire, with its large number of relatively small individual strands, is less likely to fracture from repealed flexing. Generally, for any given overall wire gage, the greater is the number of strands, the more flexible is the wire. For example, 18-gage wire can contain seven strands of 26-gage wire, 19 strands of 30-gage wire or 41 strands of 34-gage wire. For best flexibility, select wire containing the maximum number of strands for its gage.

Rope-stranded battery cable is often specified where extreme flexibility is needed to facilitate routing.

Braided ground straps, a form of cable, used to be commonly used as battery ground cable. Smaller versions are sometimes used to ground the engine to the chassis, or sheet-metal body to the chassis, if rubber mounts between these assemblies restrict electrical continuity.

Regardless of size, all wire and cables have one thing in common — they need an insulative covering to keep the electrons in their correct paths. Years ago, wire and cable insulation were made of braided cloth; today’s cars use wires with a more durable PVC plastic insulation. Several specialty houses carry cloth-insulated wire for antique or collector cars. Whether cloth or plastic, automotive wire insulation has several important characteristics.

Insulation colour is the first characteristic. Each wire of a factory-made wiring harness has its own unique colour. This was done so each circuit could be identified as the car was being built, and later for diagnosing a problem.

Sometimes, a factory-made harness has more wires in it than there are single wire colours available. In this case, the designer specifies a second color, called a tracer, which is a contrasting stripe running the length of the wire. For instance, by adding a white tracer to a red wire, you have distinguished the wire from a plain red one. Tracers are always chosen to contrast with the base colour of the insulator, and may come in a number of colors, though purple and orange tracers are rarely seen.

In designing circuit diagrams and building harnesses for your project car, you have complete control over the choice of wire colors. And, because you’re going to take extra care in constructing your harness, wire by wire, you probably won’t have much need for tracer wire.

If you must use tracer wire and you can’t find any, you can make your own by using a waterproof marking pen to draw a contrasting stripe along the length of the wire.

Another way to make a tracer, though less desirable, is to mark the terminal ends of the wires with a dab of paint. There are several disadvantages to this method. First, the paint may chip off. Second, there’s no way to distinguish the tracer wire except at the end. Third, if the wire turns out to be too long, and you cut it short, the tracer may end up on the garage floor.

Finally, labels can be purchased at many electrical-supply outlets, for the sole purpose of marking wire ends for identification purposes.

One more thing about colour: on American-built cars, black wires are almost always used on the ground (-) side of a circuit. However, in the thousands of factory harnesses made, there are probably some exceptions to this role. German cars use brown — the colour of earth (ground) — to indicate ground.

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Підготувала викладач Кудрява О.В.

Red always means hot (+) although other colours are also used for hot wires in a harness. Imagine the confusion if every feed wire in the harness was the same colour!

The red-for-positive convention also applies to the battery positive cable and battery-feed wires to the generator, fuse panel and ignition switch, in most cars, these are the wires that are always hot, even when the ignition switch is off. Again, you may find exceptions.