Charging System: Description and Operation

The charging system is a negative ground system consisting of the:
^ generator
^ integral/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 run position, 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. 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 on 3G generator models (integral mounted voltage regulator). This voltage feedback signal (typically half battery voltage) is used 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 proper 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

The optional dual generator package consists of an upper/lower dual generator system. The upper generator is a 6G 50/110 generator with a 2.49:1 pulley ratio. The lower generator is a 6G 50/110 generator with a 2.32:1 pulley ratio. Thus the upper and lower generator are not interchangeable.

This system is also monitored and controlled by the generator Powertrain Control Module (PCM). The PCM monitors both the upper and lower generator/circuits to determine both generators' output and set possible fault codes (Diagnostic Trouble Codes [DTCs]). The PCM only controls the lower generator by turning it ON or OFF by opening or closing the lower generator off only when the glow plugs are commanded on by the PCM to avoid possible damage (excessive current) to the glow plugs.

Both generators are independent of one another and only control themselves (through their own internal voltage regulator). If one generator fails, the other generator can maintain system performance under light load conditions. Under a heavy load, the PCM should detect a problem, set a DTC and illuminate the warning indicator.

The PCM controls the charging system warning indicator and will command the light on if the PCM detects a problem on the monitored circuits.

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
The I (ignition) circuit is used to turn on the voltage regulator. This circuit is powered up with the ignition key in the run position. This circuit is also used to turn the charging system warning indicator on if there is a fault in the charging system operation.

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. This circuit is also used to supply current to the generator field (rotor). The amount of current supplied to the rotor determines generator output.

S Circuit
The S circuit or stator circuit is used to feed back a voltage signal from the generator to the regulator. This voltage is used by the regulator to turn off the charging system warning indicator. The S circuit is fed back externally on integral mounted regulators on the 3G generator. This circuit is internal to the generator on internal regulator model generators such as the 6G generators.