GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual

The Charging System

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The automobile charging system provides electrical power for operation of the vehicle's ignition system, starting system and all the electrical accessories. The battery serves as an electrical surge or storage tank, storing (in chemical form) the energy originally produced by the belt driven alternator. The system also provides a means of regulating alternator output to protect the battery from being overcharged and to avoid excessive voltage to the accessories.

The storage battery is a chemical device incorporating parallel lead plates in a tank containing a sulfuric acid-water solution. Adjacent plates are slightly dissimilar, and the chemical reaction of the two dissimilar plates produces electrical energy when the battery is connected to a load such as the starter motor. The chemical reaction is reversible, so that when the alternator is producing a voltage greater than that produced by the battery, electricity is forced into the battery, and the battery is returned to its fully charged state.

The vehicle's alternator is driven mechanically, through a belt, by the engine crankshaft. The alternator consists of two coils of fine wire, one stationary (the stator), and one movable (the rotor). The rotor may also be known as the armature and consists of fine wire wrapped around an iron core which is mounted on a shaft. The electricity which flows through the two coils of wire (provided initially by the battery) creates an intense magnetic field around both rotor and stator, and the interaction between the two fields creates voltage, allowing the alternator to power the accessories and charge the battery.

All vehicles covered in this manual will be equipped with an alternating current generators or alternators because they are more efficient than the generators used in older vehicles, can be rotated at higher speeds, and have fewer brush problems. In an alternator, the field rotates while all the current produced passes only through the stator windings. The brushes bear against continuous slip rings rather than a commutator. This causes the current produced to periodically reverse the direction of its flow. Diodes (electrical one-way switches) block the flow of current from traveling in the wrong direction. A series of diodes is wired together to permit the alternating flow of the stator to be converted to a pulsating, but unidirectional flow at the alternator output. The alternator's field is wired in series with the voltage regulator.

The regulator consist of several circuits. Each circuit has a core, or magnetic coil of wire, which operates a switch. Each switch is connected to ground through one or more resistors. The coil of wire responds directly to system voltage. When the voltage reaches the required level, the magnetic field created by the winding of wire closes the switch and inserts a resistance into the generator field circuit, thus reducing the output. The contacts of the switch cycle open and close many times each second to precisely control voltage. Alternators are self-limiting as far as maximum current is concerned,

 
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