GM Service Manual Online
For 1990-2009 cars only

Starter

Battery voltage is available at all times through Maxi-Fuse located in the Underhood Fuse-Relay Center. Voltage is made available at the ignition switch through the RED (242) wire. When the ignition switch is placed in START, contacts in the switch close in order to apply voltage to the YEL (5) wire. The YEL (5) wire terminates at PIN A of the Clutch Pedal Position Switch for Manual Transmission or at PIN E of the Transmission Range Switch for Automatic Transmission.

If the clutch pedal is depressed for Manual Transmission or if the Automatic Transmission is in the PARK or NEUTRAL position, contacts are closed which applies voltage to the PPL (1035) wire at PIN B of the Clutch Start Switch or at PIN G of the Park/Neutral Position Switch. The PPL (1035) wire applies voltage to PIN B9 and to PIN A7. The BLK (150) wiring from PIN A7 provides a ground path to ground G105 and the starter relay coil is energized.

When the relay coil is energized, contacts are closed to apply, battery voltage to the starter solenoid. The RED (242) wire from Maxi-Fuse 6 to PIN A9 of the starter relay provides voltage which is sent through the PPL wire connected at Relay PIN B7 to starter solenoid Terminal S. This provides voltage to the hold-In winding and the pull-In winding of the 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 in the plunger. The plunger moves the shift lever. This action causes the starter drive assembly to rotate as it engages 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 supplied directly to the starter motor and it cranks the engine.

As soon as the solenoid switch contacts close, voltage is no longer supplied through the pull-in windings, since battery voltage is supplied 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 PPL wire and the junction of the two windings. Voltage is supplied from the motor contacts through both windings to ground at the end of the hold-in windings. However, the voltage supplied to the pull-in winding is now opposing the voltage supplied when the winding was first energized. The magnetic fields of the pull-in and hold-in windings now oppose one another. This action the windings, with the help of the return spring, causes the starter drive assembly to disengage and 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's electrical system and the 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 by the rectifier bridge and is supplied to the electrical system at the battery terminal.

This generator's regulator uses digital techniques to supply the rotor current and thereby controlling the output voltage. The rotor current is proportional to the width of the electrical pulses supplied to it by the regulator. When the ignition switch is place in RUN, 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 the electrical system operation.

Starter and Charging

The digital regulator controls the BAT Indicator lamp with a solid-state lamp driver. The lamp driver turns on the lamp whenever undervoltage, overvoltage, or a stopped generator is detected.

Voltage is available to the indicator lamp and the generator when the ignition switch is in RUN, Bulb Test, or START. The 20 Amp Gauges Fuse 4 located in the I/P Fuse Block provides voltage though the PNK (39) wire to Instrument cluster PIN 22. Then there is no current flowing battery voltage is available at PIN 19 and is provided the generator through the VRN (25) wire. Generator Connector Cavity B connects to Generator PIN L. This voltage input provides operating power for the regulator when the engine is running and generator voltage is too high or too low. This voltage input is grounded by contacts within the regulator. This switch closure allows current to flow which causes the BAT indicator to light.

For vehicles with the diesel engine, the tachometer input is sensed at PIN P of the generator. Generator Connector Cavity A connects to generator PIN P to send the pulsing voltage signal to PIN 6 of the instrument cluster though the WHT (121) wire. the instrument cluster converts the voltage frequency to engine RPM.