Charging System: Description and Operation
CHARGING SYSTEMThe charging system is a negative ground system consisting of the following components:
- Generator(s)
- Internal voltage regulator
- Charging system warning indicator
- Battery
- Circuitry and cables
Generator(s)
The generator(s) is belt-driven by the engine accessory drive system.
Single Generator
The single generator system consists of the generator mounted on the top right of the engine (diesel) or top center of the engine (gas). The gas engines use a 115-amp generator with a 2.52:1 pulley ratio. An extra heavy-duty option is available. For 5.4L and 6.8L gas engines, it includes a 135-amp generator with a 2.52:1 pulley ratio. The 6.0L diesel engine uses a 110-amp generator with a 2.79:1 pulley ratio.
An extra heavy-duty option is available for the 6.0L diesel. It includes a 140-amp generator with a 2.79:1 pulley ratio. The generators are similar in appearance and use the same connectors, making them interchangeable. Identification between the different generators can be carried out by referring to the generator engineering number and the parts catalog.
In the single generator system, with the key in the ON position, voltage is supplied through the charging system warning indicator (in the instrument cluster) through the I circuit to the voltage regulator. The regulator grounds this circuit and the charging system warning indicator is illuminated. When the engine is started, the regulator removes the ground on this circuit and the charging system warning indicator turns off.
Dual Generator
The dual generator package consists of an upper/lower generator system (diesel only). The 6.0L upper generator is a 140-amp generator with a 2.79:1 pulley ratio. The 6.0L lower generator is a 120-amp generator with a 3.00:1 pulley ratio. The upper and lower generators are not interchangeable.
The dual generators operate independently of each other. The control is through the internal voltage regulators. If one generator fails, the other generator can maintain system performance under light load conditions. Under a heavy load, the powertrain control module (PCM) detects a concern, sets a diagnostic trouble code (DTC), and illuminates the charging system warning indicator.
On the dual generator system, the PCM controls the charging system warning indicator and commands the lamp on if the PCM detects a concern on the monitored circuits.
The dual generator system is also monitored and controlled by the PCM. The PCM monitors both the upper and lower generator I circuits to determine the output of both generators and sets possible DTCs. The PCM controls the lower generator by turning it off when the glow plug system is commanded on by the PCM to avoid possible damage (excessive voltage) to the glow plugs. As soon as the glow plug system stops cycling, the PCM powers up the lower generator.
The set voltage varies 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.