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11:25 AM
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Chapter Six
Figure 6-11.
Assorted battery cables.
years, however, high-resistance, non-metallic cables have replaced metallic conductor cables as original equipment on cars and light trucks. Although metallicconductor ignition cables are still made, they are sold for special high-performance or industrial applications and are not recommended for highway use. The conductors used in high-resistance, nonmetallic ignition cables are made of carbon, or of linen or fiberglass impregnated with carbon. These cables evolved for the following reasons: • High-voltage ignition pulses emit high-fre-
quency electrical impulses or radio frequency interference (RFI) that interfere with radio and television transmission, as described in Chapter 2. The principal method used to limit this interference is the use of high-resistance ignition cables, often referred to as suppression cables. • The extra resistance in the cable decreases the current flow and thus reduces the burning of spark plug electrodes. The higher resistance also helps take advantage of the high-voltage capabilities of the ignition system, as shown in Part Five of this manual. The high-voltage current carried by ignition cables requires that they have much thicker insulation than low-voltage primary wires. Ignition cables are 7 or 8 millimeters in diameter, but the conductor in the center of the cable is only a small core. The rest of the cable diameter is the heavy insulation used to contain the high voltage and protect the core from oil, dirt, heat, and moisture. One type of cable insulation material is known by its trade name, Hypalon, but the type most commonly used today is silicone rubber. Silicone is generally thought to provide greater high-voltage
insulation while resisting heat and moisture better than other materials. However, silicone insulation is softer and more pliable than other materials and thus more likely to be torn or damaged by rough handling. Cables often have several layers of insulation over the conductor to provide the best insulating qualities with strength and flexibility.
CONNECTORS AND TERMINALS Electrical circuits can be broken by the smallest gap between conductors. The gaps can be caused by corrosion, weathering, or mechanical breaks. One of the most common wear points in an automobile electrical system is where two conductors have been joined. Their insulation coats have been opened and the conductive material exposed. Special connectors are used to provide strong, permanent connections and to protect these points from wear. These simple connectors are usually called wiring terminals. They are metal pieces that can be crimped or soldered onto the end of a wire. Terminals are made in many shapes and sizes for the many different types of connections required. They can be wrapped with plastic electrical tape or covered with special pieces of insulation. The simplest wire terminals join a single wire to a device, to another single wire, or to a few other wires (Figure 6-12). Terminals for connecting to a device often have a lug ring, a spade, or a hook, which can be bolted onto the device. Male and female spade terminals or bullet connectors are often used to connect two individual wires
