Principles of Operation

PRINCIPLES OF OPERATION

After the engine is started, voltage is applied through the I (ignition) circuit 904 (LG/RD) from the powertrain control module (PCM) to the voltage regulator. This turns the regulator on, allowing current to flow from the A (battery sense) circuit 35 (OG/LB) to the generator field coil. At this time, the generator begins to generate current, which is then supplied to the vehicle electrical system through the output (B+) terminal of the generator.

Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the regulator. This voltage feedback signal (typically half the battery voltage) is used by the regulator to provide a signal to the PCM. This, in turn, provides a signal over the controller area network (CAN) communication link to the instrument cluster to turn off the charging system warning lamp. This indicates the charging system is operating properly. The S (stator) circuit is internal to the generator on 4.6L applications, but is an external circuit 4 (WH/BK) on 4.0L applications.

With the system functioning normally, the generator output current is determined by the voltage of the A circuit 35 (OG/LB). The A circuit 35 (OG/LB) voltage is compared to a set voltage internal to the regulator. The regulator controls the generator field current to maintain the correct generator output.

The set voltage varies with temperature and is typically higher in cold temperatures and lower in warm temperatures. This allows for better battery recharge in the winter and reduces the possibility of overcharging in the summer.

Battery Positive Output (B+) Circuit 38 (BK/OG)
The generator output is supplied through the battery positive output (B+) terminal circuit 38 (BK/OG) on the rear of the generator to the battery and electrical system. I Circuit 904 (LG/RD)

I Circuit 904 (LG/RD)
The I circuit 904 (LG/RD) is used to turn on the voltage regulator. This circuit is powered by the PCM after the engine is started. This circuit is also used by the PCM to determine whether or not to send a message over the CAN communication link to the instrument cluster to turn the charging system warning indicator on if there is a fault in the charging system operation. If there is a fault in the charging system operation, the regulator grounds the I circuit, the PCM senses a voltage drop on the I circuit and sends a message over the CAN communication link to the instrument cluster to cause the charging system warning indicator to illuminate.

S Circuit 4 (WH/BK) (4.0L vehicles)
The S circuit 4 (WH/BK) (external only on 4.0L vehicles, internal on 4.6L vehicles) is used to feed back a voltage signal from the generator stator to the regulator. This voltage feedback signal (typically half the battery voltage) is used by the regulator to determine when to open the grounded I circuit 904 (LG/RD) to the PCM. The PCM, in turn, provides a signal over the CAN communication link to the instrument cluster to turn off the charging system warning lamp indicating the charging system is operating properly.

A Circuit 35 (OG/LB)
The A circuit 35 (OG/LB) is used to sense battery voltage. This voltage is used by the regulator to determine generator output. This circuit is used to supply current to the generator field (rotor). The amount of current supplied to the rotor determines the generator output.