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CHARGING CIRCUIT
The charging circuit supplies the proper amount of current for the car's lights, ignition system, radio, heater, and other electrical accessories. Also, it must maintain the battery in a charged state, and recharge it when necessary. This system has four basic components: The battery, the generator or alternator, the voltage regulator, and various cables and wires. The battery's functions are twofold. The previous chapter discussed its role as a supplier of electrical power for the starter motor and the ignition system while the engine is cranking. In addition, the battery must supply additional current for the car's electrical devices when the generator or alternator output cannot meet the electrical demand. On a cold, rainy night, for example, let's say your car is stopped at a traffic light. In this situation, the lights, heater, windshield wipers, ignition system, and radio all may be in operation. If the generator or alternator is not able to put out all the energy needed, the battery must make up the deficiency.
The generator or alternator is a mechanical device which converts mechanical energy into electrical energy. The mechanical energy comes from the engine via the fan belt. The electrical energy thus produced operates the car's electrical devices. The generator or alternator, when functioning properly, will meet all of the electrical requirements of the car at any speed. The principal difference between the generator and the alternator is the output at engine curb idle speed and slightly above. The alternator's output is higher, and this is the primary reason it has supplanted the generator in today's cars. On the other hand, one advantage the generator has over the alternator is that it does not need electricity to make electricity. The alternator does. In other words, the generator is "self-exciting," which means it is able to create electricity simply by turning about 600 revolutions per minute (RPM) with no electrical input.
When an alternator or generator is used, its electrical output must be controlled. If not, the enormous voltage generated would destroy the car's electrical devices. The voltage regulator is the control unit, regulating the generator or alternator output to a value preset by the manufacturer, which protects the battery and electrical accessories from high-voltage damage.
The car has either an ammeter or an indicator light on the dash-board indicating whether or not the charging system is operating trouble-free. Cables and wires are necessary to complete the circuits between the components. These must be kept in good condition. This means no loose or dirty connections, no exposed wires, and no frayed insulation.
In this chapter you will learn how to test and replace each component of the charging circuit. Although generators are something of a dying breed, there are still enough of them in use today to make discussion of them helpful.
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