Diagnosing Charging System Problems From Toyota Motor Sales, U.S.A. The automotive charging system con- verts mechanical energy into electrical energy when the engine is running. This energy is needed to operate the loads in the vehicle’s electrical system. When the charging system’s output is greater than that needed by the vehicle, it sends cur- rent into the battery to maintain the bat- tery’s state of charge. Proper diagnosis of charging system problems requires a thorough understanding of the system components and their operation. When the engine is running, battery power energizes the charging system and engine power drives it. The charging system then generates electricity for the vehicle’s electrical systems. At low speeds with some electrical loads “on” (e.g., lights and window defogger), some battery current may still be needed. But at high speeds, the charging system sup- plies all the current needed by the vehi- cle. Once those needs are taken care of, the charging system then sends current into the battery to restore its charge. Toyota Charging Systems Typical charging system components include: Ignition switch: When the ignition switch is in the ON position, battery current energizes the alternator. Alternator: Mechanical energy is transferred from the engine to the alter- nator by a grooved drive belt on a pulley arrangement. Through electromagnetic induction, the alternator changes this mechanical energy into electrical energy. The alternating current generated is con- verted into direct current by the rectifier, a set of diodes which allows current to pass in only one direction. Voltage regulator: Without a regula- tor, the alternator will always operate at its highest output. This may damage certain components and overcharge the battery. The regulator controls the alter- nator output to prevent overcharging or undercharging. On older models, this is a separate electromechanical compo- nent which uses a coil and contact points to open and close the circuit to the alternator. On most models today, this is a built-in electronic device. REGULATOR ALTERNATOR BATTERY J yacaton Sy IGNITION ELECTRIC CHOKE HEATING COIL VEHICLE LOADS Battery: The battery supplies current to energize the alternator. During charg- ing, the battery changes electrical energy from the alternator into chemical energy. The battery’s active materials are restored. The battery also acts as a “shock absorber” or voltage stabilizer in the sys- tem to prevent damage to sensitive com- ponents in the vehicle’s electrical system. Indicator: The charging indicator device most commonly used on Toyotas is a simple on/off warning lamp. It is nor- mally off. It lights when the ignition is turned on for a check of the lamp circuit. And it lights when the engine is running if the charging system is undercharging. A voltmeter is used on current Supra and Celica models to indicate system voltage. It is connected in parallel with the battery. An ammeter in series with the battery was used on older Toyotas. Fusing: A fusible link as well as sep- arate fuses are used to protect circuits in the charging system. Alternator Construction Two different types of alternators are used on Toyota vehicles. A convention- al alternator and separate voltage regu- lator were used on all Toyotas prior to 1979. A new compact, high-speed alter- nator with a built-in IC regulator is now used on most models. Both types of alternators are rated according to current output. Typical ratings range from 40 amps to 80 amps. A conventional alternator is currently used on some 1986 Tercel models, and all Toyotas prior to 1979. Beginning with the 1983 Camry, a compact, high-speed alternator with a built-in IC regulator is used on Toyota vehicles. Corolla models with the 4A-C engine use a different alternator with an integral IC regulator.