GM Service Manual Online
For 1990-2009 cars only

Starter

When the Ignition Switch is moved to START, the battery voltage is applied to the Starter Solenoid. Both Solenoid Windings are energized. The circuit through the Pull In Winding is completed to ground through the Starter Motor. The Windings work together magnetically to pull in and hold the Plunger. The Plunger moves the Shift Lever. This action causes the Drive Assembly to rotate as it engages with the Flywheel ring gear on the engine. At the same time, the Plunger also closes the solenoid switch contacts in the Starter Solenoid. Full battery voltage is applied directly to the Starter Motor and it cranks the engine.

As soon as the solenoid contacts close, voltage is no longer applied through the Pull in Winding, since battery voltage is applied to both ends of the Windings. The Hold In Winding remains energized, and its magnetic field is strong enough to hold the Plunger, Shift Lever, and Drive Assembly Solenoid switch contacts in place to continue cranking the engine.

When the ignition switch is released from the START position, battery voltage is removed from the Starter Solenoid and the junction of the two Windings. Voltage is applied from the motor contacts through both Windings to ground at the end of the Hold in Winding. However, the voltage applied to the Pull in Winding is now opposing the voltage applied when the Winding was first energized. The magnetic fields of the Pull in and Hold in Windings now oppose one another. The Return Spring then causes the Drive Assembly to disengage and the solenoid switch contacts to open simultaneously. As soon as the contacts open, the starter circuit is turned OFF.

Charging

The Generator provides voltage to operate the vehicle electrical system and to charge its battery. A magnetic field is created when current flows through the Rotor. This field rotates as the Rotor is driven by the engine, creating an AC voltage in the Stator Windings. The AC voltage is converted to DC voltage by the Rectifier Bridge, and is supplied to the electrical system at the battery terminal. The Generator's Regulator uses digital techniques to supply the Rotor current and thereby control the output voltage. The Rotor current is proportional to the width of the electrical pulse supplied by the Regulator. When the Ignition Switch is placed in the RUN position, voltage is supplied to terminals L and F, turning on the Regulator. Narrow width pulses are supplied to the Rotor creating a weak magnetic field. When the engine is started, the Regulator senses Generator rotation by detecting AC voltage at the Stator through an internal wire. Once the engine is running, the Regulator varies the field current by controlling the pulse width. This regulates the Generator output voltage for proper Battery charging and electrical system operation. The Regulator sends output to the PCM which lights the Volts telltale if a fault is detected.