Toyota Wire, Terminal and Connector Repair

Reversed polarity may damage alternator diodes, cause improper operation of the ignition coil and spark plugs, and may damage other devices …

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Conductors are needed to complete the path for electrical current to flow from the power source to the working devices and back to the power source.

Special wiring is needed for battery cables and for ignition cables. Battery cables are usually very thick, stranded wires with thick insulation. Ignition cables usually have a conductive carbon core to reduce radio interference. GROUND PATHS Wiring is only half the circuit in Toyota electrical systems. This is called the \”power\” or insulated side of the circuit. The other half of the path for current flow is the vehicle\’s engine, frame, and body. This is called the ground side of the circuit. These systems are called single-wire or ground-return systems. A thick, insulated cable connects the battery\’s positive ( + ) terminal to the vehicle loads. As insulated cable connects the battery\’s negative ( – ) cable to the engine or frame. An additional grounding cable may be connected between the engine and body or frame. Resistance in the insulated side of each circuit will vary depending on the length of wiring and the number and types of loads. Resistance on the ground side of all circuits must be virtually zero. This is especially important: Ground connections must be secure to complete the circuit. Loose or corroded ground connections will add too much resistance for proper circuit operation. SYSTEM POLARITY System polarity refers to the connections of the positive and negative terminals of the battery to the insulated and ground sides of the electrical system. On Toyota vehicles, the positive (+) battery terminal is connected to the insulated side of the system. This is called a negative ground system having positive polarity. Knowing the polarity is extremely important for proper service. Reversed polarity may damage alternator diodes, cause improper operation of the ignition coil and spark plugs, and may damage other devices such as electronic control units, test meters, and instrument panel gauges.
POWER OR INSULATED CONDUCTORS Conductors for the power or insulated current path may be solid wire, stranded wire, or printed circuit boards. Solid, thin wire can be used when current is low. Stranded, thick wire is used when current is high. Printed circuitry – copper conductors printed on an insulating material with connectors in place – is used where space is limited, such as behind instrument panels. P age 1 (c) Toyota Motor Sales, U.S.A., Inc. All Rights Reserved.
HARNESSES Harnesses are bundles of wires that are grouped together in plastic tubing, wrapped with tape, or molded into a flat strip. The colored insulation of various wires allows circuit tracing. While the harnesses organize and protect wires going to common circuits, don\’t over look the possibility of a problem inside.
WIRE INSULATION Conductors must be insulated with a covering or \”jacket.\” This insulation prevents physical damage, and, more important, keeps the current flow in the wire. Various types of insulation are used depending on the type of conductor. Rubber, plastic, paper, ceramics, and glass are good insulators.
CONNECTORS Various types of connectors, terminals, and junction blocks are used on Toyota vehicles. The wiring diagrams identify each type used in a circuit. Connectors make excellent test points because the circuit can be \”opened\” without need for wire repairs after testing. However, never assume a connection is good simply because the terminals seem connected. Many electrical problems can be traced to loose, corroded, or improper connections. These problems include a missing or bent connector pin.
The repair parts now in supply are limited to those connectors having common shapes and terminal cavity numbers. Therefore, when there is no available replacement connector of the same shape or terminal cavity number, please use one of the alternative methods described below. Make sure that the terminals are placed in the original order in the connector cavities, if possible, to aid in future diagnosis. 1 . When a connector with a different number of terminals than the original part is used, select a connector having more terminal cavities than required, and replace both the male and female connector parts. Example: You need a connector with six terminals, but the only replacement available is a connector with eight terminal cavities. Replace both the male and female connector parts with the eight terminal part, transfering the terminals from the old connectors to the new connector. 2. When several different type terminals are used in one connector, select an appropriate male and female connector part for each terminal type used, and replace both male and female connector parts. Example: You need to replace a connector that has two different types of terminals in one connector. Replace the original connector with two new connectors, one connector for one type of terminal, another connector for the other type of terminal.
Conductor repairs are sometimes needed because of wire damage caused by electrical faults or by physical abuse. Wires may be damaged electrically by short circuits between wires or from wires to ground. Fusible links may melt from current overloads. Wires may be damaged physically by scraped or cut insulation, chemical or heat exposure, or breaks caused during testing or component repairs.

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