Principles of Operation: Notes

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

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.