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 510 ohms 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.