Principles of Operation

PRINCIPLES OF OPERATION

Charging System
After the engine is started, voltage is applied through the I circuit 1931 (BN/PK) from the powertrain control module (PCM) to the generator. This turns the regulator on, allowing current to flow from the battery sense A circuit 35 (OG/LB) to the generator field coil. When the engine is started, the generator begins to generate alternating current (AC) which is internally converted to direct current (DC). This current 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 internally. This voltage feedback signal (typically half the 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 35 (OG/LB) which is compared to a set voltage internal to the regulator. The regulator controls the generator field current to maintain the current generator output.

The set voltage will vary with temperature and is typically higher in cold temperatures and lower in warm temperatures. This allows improved battery recharge in the winter and reduces the chance of overcharging in the summer.

Circuit Description

B+ Output Terminal Circuit 38 (BK/OG)
Generator output voltage is supplied through the battery positive (B+) output terminal on the rear of the generator to the battery and the electrical system.

Circuit 35 (OG/LB)
This is the A-line battery voltage sense circuit and is used to sense battery voltage.

Circuit 1930 (TN/LG)
The PCM determines the optimal voltage setpoint for the charging system and communicates the information to the voltage regulator via the Alternator Load Feed Forward (ALFF) circuit. This is a communication line only and can only be measured with an ohmmeter.

Circuit 1931 (BN/PK)
The I-line circuit is used to turn on the voltage regulator. This circuit is powered by the PCM with the engine running. This circuit is also used by the PCM to determine if and when to send a message to the instrument cluster to turn the charging system warning indicator on if there is a fault in the charging system.