Starting and Charging Circuit General Description

The Engine Electrical System consists of portions of the Ignition Systems, the Engine Electrical Power Distribution System, and the Starter and Charging System. The Ignition Systems through the ignition control modules are described in the Engine Controls sections. The Engine Electrical Power Distribution System includes the Battery and those wires and components which distribute power to the I/P Fuse Block or to the unfused loads. The Battery, the Power Distribution Center, and the Ignition Switch are the major system components. Fusible links are employed to provide circuit protection for the Battery leads and for major power distribution branch loads. Fuses or circuit breakers provide circuit protection to the various sub-systems. The Starting and Charging System is discussed below.

The Starter and Charging System is discussed as two sub-systems. These are the Charging System and the Starting System. The Charging System provides current to the Battery while the engine is operating in order to maintain the Battery in a charged condition. The Charging System operates to keep the Battery voltage between 13 and 16 volts. Sufficient current is produced by the system to operate all normal loads while maintaining the Battery's charge. The Charging System consists of one major component. This is the Generator. A Battery Indicating Lamp is provided on the Instrument Cluster. The lamp warns the driver of abnormal conditions in the Charging System. A Voltmeter is also provided on the Instrument Cluster. This provides a reasonably accurate analog indication of Battery voltage.

The Starting System is used to start the engine. The system uses battery power to energize the Starter Solenoid and to drive the Starter Motor. The Starter Solenoid engages the starter's drive gear with the engine's flywheel in order to rotate or crank the engine. At the same time, battery power is applied to the Starter Motor which then drives the flywheel allowing the engine to start. Once the engine is started, the Starter is disengaged. The engine continues to operate on it's own power.

Starting and Charging Circuit Charging System Operation

The Generator provides voltage to operate the vehicle's electrical systems and to charge the Battery. The Generator is driven by a serpentine drive belt which is driven by the engine. As the engine starts, the generator begins to rotate. The mechanical energy provided by the operation of engine is converted to electrical energy by the Generator.

When the Ignition Switch is returned to the Run position after the engine has started, battery voltage is applied from GAUGES Fuse 4 to the Generator. This voltage is first routed to the Instrument Cluster on the PNK (39) wire. It passes through the Instrument Cluster through the Battery Indicator Lamp and through the resistor which is in parallel with the lamp. From the Instrument Cluster, the voltage is applied to the Generator through the BRN (25) wire.

The Generator is equipped with a solid state voltage regulator. The voltage regulator converts the battery voltage to a sequence of voltage pulses which are applied to the Generator's rotor or field winding. This creates a pulsing magnetic field in the rotor. The pulses are timed by the regulator to coincide with the rotation of the rotor. Since the rotor is rotating, this causes the rotating magnetic field to pass through the electrical conductors in the stator. The effect of this rotating magnetic field is to generate an induced voltage in the stator. The induced voltage in the stator is greater than the voltage in the rotor because of the difference in the number of windings. The stator has a greater number of windings and a greater voltage is induced because of this.

The induced voltage is fed to a Rectifier Bridge. The diodes in the Rectifier Bridge allow current to flow from the Generator only when the polarity of the voltage will add to the voltage in the battery. Current leaves the Generator through the Generator's battery terminal to supply any electrical loads and to charge the Battery.

The voltage at the Generator's battery terminal is sensed by the voltage regulator. The regulator uses this feedback information to change the width of voltage pulses that it feeds to the rotor. This, in turn, changes the output current and the output voltage. The voltage regulator thus regulates the Generator's terminal voltage at approximately 14  volts. The charging voltage may range between 13 and 16  volts and still be in an acceptable range.

This voltage is adequate to overcome the static 12  volt rating of the battery. This causes some charging current to flow through the battery. The charging current causes a chemical reaction to occur in the battery. The chemical reaction stores electrical energy as chemical energy. When the engine is started, the chemical reaction is reversed and electrical energy is made available to drive the Starter. It is this charging chemical reaction that releases hydrogen. Hydrogen is potentially explosive. This service manual includes a battery caution at appropriate places to warn of this potential danger.

When electrical loads other than the battery are applied, the Generator terminal voltage tends to decrease. The voltage regulator senses this decrease in voltage and compensates for it. It increases the voltage pulses at the rotor in order to maintain terminal voltage in the desired range. When the electrical load is reduced, the regulates again adjusts terminal voltage to be within range.

If the regulator is unable to keep the terminal voltage in the required range, a warning is provided to the driver. The Battery Indicating Lamp on the Instrument Cluster is illuminated. The Generator grounds the BRN (25) wire through internal contacts to provide a current path to light the lamp. If this lamp is illuminated while the engine is running, the driver is alerted to a potential malfunction in the charging system. Aftermarket equipment may demand so much current that the Generator cannot supply all of the load. Aftermarket equipment should be disconnected and the Charging System's operation checked without the extra load before repairs are performed.

The Battery Indicating Lamp also provides a warning indication when the Ignition Switch is in the Run position but the Generator is not rotating. Mechanical failure of the drive belt or the Generator may prevent the Generator from rotating. If the engine has not yet been started, the illumination of the lamp serves as a bulb check. The 510ohms resistor that is installed in parallel with the Battery Indicating Lamp provides an alternate voltage path to the Generator if the Battery Indicating Lamp's filament has opened. The Generator receives enough voltage through this bypass to continue operation.

Starting and Charging Circuit Starting System Description

The Ignition Switch is a multi-contact rotary switch containing five layers or sets of contacts. As the ignition key is rotated, various contacts in the five layers operate to open or to close. The contact development for each switch layer depends upon the position of the rotary switch. The switch has four maintained contact positions and one momentary contact position. These five positions are the Accessory (ACC) position, the Lock position, the Off position, the Run position, and the Start position. The Start position is the momentary contract position. The Start position is only operated by holding the ignition key in place. These five switch positions control the operation of the ignition circuits. Refer to the schematic in SECTION 8A-10.

The ACC position is used to operate either the radio, the wipers, or the overhead map lamps while all other ignition circuits remain de-energized. These components are also available with the Ignition Switch in the Run position.

The Lock position is the position in which the Ignition Key may be removed from the Ignition Switch. Otherwise, it is identical to the Off position.

The Off position is the position in which all ignition circuits are de-energized. However, the Ignition Key cannot be removed from the Ignition Switch while in this position.

The Run position energizes all ignition circuits with the single exception of the Start or Crank circuit. The Run position is the switch position used while the vehicle is operating. Refer to the schematics in SECTIONS 8A-10 and 8A-11.

The Start position is sometimes addressed as the Crank position. In this position, the Starter is energized in order to start the engine. Depending upon the vehicle's options, this position also sends signals to various control modules. Refer to the schematic in SECTION 8A-11. These signals inform the control modules that the engine is being started. The function of these signals is described in the appropriate system description.

Some electrical loads are operated with the Ignition Switch in either the Run or the Crank position. The switch contacts for these loads do not open as the Ignition Switch is moved between the Run and the Start contacts. Voltage continuity is maintained. Refer to the schematic in SECTION 8A-10.

There is no Bulb Test position. However, not all of contact layers may operate at the same time. Four of the sets of contacts are closed in the Run position. By moving the key slowly from the Off position, it is possible that some of the Ignition circuits will be energized before the others. However, it is not necessary to do this as the bulb check function is fully demonstrated by the electrical systems while the Ignition Switch is in the Run position. The bulb check functions are described in the appropriate system descriptions.

Starting and Charging Circuit Starting System Operation

Voltage is available at all times through the BLK (2) fusible link at the Battery Junction Block and the RED (1442) wire to the Ignition Switch. When the Ignition Switch is held in the Start position, battery voltage is applied to the YEL (5) wire to the I/P Fuse Block. CRANK Fuse 20, if it remains continuous (not open) , supplies this voltage through the PPL (806) wire to either the Transmission Range Switch (Park/Neutral Position And Backup Lamp Switch) for vehicles with automatic transmissions. If the vehicle has a manual transmission, the voltage is applied to the Clutch Pedal Position And Cruise Control Shutoff Switch.

The contacts in the Transmission Range Switch (Park/Neutral Position And Backup Lamp Switch) are closed when the automatic transmission is in either the Park or the Neutral position. With the contacts closed, battery voltage is applied on the YEL (1737) wire to the coil of the Starter Relay at Pin 85.

The contacts in the Clutch Pedal Position And Cruise Control Shutoff Switch are closed when the clutch pedal is depressed. With the contacts closed, battery voltage is applied on the PPL/WHT (1035) wire to the coil of the Starter Relay at Pin 85.

The Starter Relay's coil is grounded from Pin 86 by the BLK (150) wire to the engine grounds. With voltage applied at Pin 85, the Starter Relay coil energizes and closes the relay contacts. Battery voltage is available at all times from the Generator terminal through the RED (1542) wire and the BLK (1542) fusible Link. When the relay's contacts close, battery voltage is applied on the PPL (6) wire to Terminal S of the Starter Solenoid.

The Starter Solenoid has two coils or windings. The Hold-In Winding is grounded at the mounting bolts. The Pull-In Winding is grounded through the Starter Motor. Both windings are energized when voltage is initially supplied from the Starter Relay. The combined force of these windings operates the solenoid plunger to move the shift lever mechanism. The movement of the shift lever mechanism engages the Starter Motor with the flywheel ring gear. This mechanical operation is described more completely in the description of the Starter.

At the same time that the solenoid plunger is operated, contacts with the solenoid close. Battery voltage is available at all times to these contacts from the Battery through the BLK (1) wire. This wire at Terminal B of the solenoid is sized to handle the current flow needed to start the engine. The closure of the solenoid's contacts applies battery voltage at rated current to the Starter Motor. The Starter Motor then operates to rotate or crank the engine.

The presence of this battery voltage applied directly to the Starter Motor through the solenoid's switch contacts causes the solenoid's Pull-In Winding to de-energize. Battery voltage is now available at both sides of this coil and no current will flow. However, the Hold-In Winding remains energized until the Ignition Switch is released from the Start position. When the engine starts, the driver releases the Ignition Switch and the Ignition Switch returns to the Run position. This removes the voltage from the Hold-In Winding and the solenoid's plunger retracts. This, in turn, disengages the Starter Motor from the flywheel. At the same time, the solenoid's contacts open. This removes battery voltage from the Starter Motor and the Starter Motor stops operating.

Starting and Charging Circuit Ignition System Coverage

The 2.2L Engine Controls section describes the ignition system to the Electronic Ignition Control Module (Without Coil) including the two Ignition Coils (Distributorless). Engine Electrical Section coverage begins at the spark plug wires. The 4.3L Engine Controls section describes the ignition system to the Electronic Ignition Control Module (Electronic Spark Control). Engine Electrical Section coverage begins at the wire to the Ignition Coil.