Charging System: Description and Operation: Description and Operation
The charging system is a negative ground system consisting of the following:^ generator(s)
^ internal voltage regulator
^ charging system warning indicator storage battery
^ necessary wiring and cables
The generator is belt-driven by the engine accessory drive system.
With the ignition key in the ON position (single generator system only), voltage is applied through the warning indicator I circuit to the voltage regulator. This turns the regulator on, allowing current to flow from battery sense A circuit to the generator field coil. The dual generator system (with the ignition key in the ON position) applies voltage through the Powertrain Control Module (PCM)-controlled I circuits (1183 [WH/YE], upper generator; 1185 [YE], lower generator) to both generators. Once the PCM sees a voltage drop on the lower generator, it turns off the voltage to the lower generator if the glow plug system is cycling. Once the glow plug system stops cycling, the PCM applies voltage to the lower generator, which turns the regulator on allowing current to flow from the battery sense A circuit to the generator field coil; at which time it begins to function normally. The PCM maintains voltage (on the I circuit) to the upper generator at all times (key ON, engine off or running). This turns the upper generator regulator on, allowing current to flow from the battery sense A circuit to the generator field coil. When the engine is started, the generator begins to generate Alternating Current (AC) which is converted to Direct Current (DC) internally. This current is then supplied to the vehicle's electrical system through the output terminal (B+) of the generator.
Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the regulator S circuit. This voltage feedback signal (typically half battery voltage) is used to turn off the warning indicator on the single generator system while on the dual generator system, the PCM uses this signal to determine when to turn off the warning indicator.
With the system functioning normally, the generator output current is determined by the voltage of the A circuit. This A circuit voltage (battery sense circuit) is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain correct generator output.
The set voltage will vary with temperature and is typically higher in cold temperatures than in warm temperatures. This allows for better battery recharge in the winter and reduces the chance of overcharging in the summer.
The battery is a 12 volt direct current source connected in a negative ground system. The battery case is sealed and includes two vent holes to release gases. The battery has three major functions:
^ engine cranking power source
^ voltage stabilizer for the electrical system
^ temporary power when electrical loads exceed the generator output current
Circuit Description
Battery Output Terminal (B+)
The generator output is supplied through the battery positive output (B+) terminal on the back of the generator to the battery and electrical system.
I Circuit - Single Generator
The I (ignition) circuit is used to turn on the voltage regulator. This circuit is powered up when the ignition switch is in the ON position. Voltage is supplied from the ignition switch to the Central Junction Box (CJB) fuse 45 (10A), then to the instrument cluster and through the charge warning indicator (battery icon) to the generator. This circuit is also used to turn the charging system warning indicator on if there is a fault in the charging system operation.
I Circuit - Dual Generator
The I (ignition) circuit is used to turn on the voltage regulator(s). This circuit is powered up when the ignition switch is in the ON position. When the PCM detects ignition ON, the PCM will provide power to the upper generator I circuit 1183 (WH/YE) and also to the lower generator I circuit 1185 (YE). The power to the lower generator will only be momentary unless the glow plug system is not cycling. Once the glow plugs stop cycling, the PCM will provide constant power on the lower generator I circuit 1185 (YE).
A Circuit
The A circuit or battery sense circuit is used to sense battery voltage. This voltage is used by the regulator to determine generator output.