Pontiac Fiero 1988 Service Manual page 994

S T A R T E R AND CHARGING S Y S T E M I
V6
V I N
9
A N D
L4
V I N R
5
CIRCUIT OPERATION
STARTER
With the Ignition Switch moved to the START
position, battery voltage is applied through the
Gear Selector Switch or the Clutch Start Switch
to the Starter Solenoid. Both the Pull-In and
Hold-In Windings are energized. They pull a
plunger into their core. The plunger is attached to
the shift lever, which drives a small pinion gear in
the drive mechanism to engage the flywheel gear
on the engine. The pinion also starts turning
since the Pull-In Winding circuit passes through
the Starter Motor. The turning gear meshes
smoothly with the flywheel.
The plunger in the Solenoid windings also
closes the Motor Contacts. These contacts connect
the battery voltage directly to the Starter Motor.
The Motor cranks the engine.
As soon as the Motor Contacts close, battery
voltage is applied to both ends of the Pull-In
Winding. Current no longer flows through the
Winding. The Hold-In Winding remains ener-
gized. Its magnetic field is strong enough to hold
the shift lever, drive mechanism, and Motor Con-
tacts 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 Wind-
ings. Current flows from the Motor Contacts
through both Windings to ground at the end of the
Hold-In Winding. However, the direction of the
current flow through the Pull-In Winding is now
opposite to the direction current flowed when the
Winding was first energized. The magnetic fields
of the Pull-In and Hold-In Windings now oppose
one another. This helps to quickly release the
spring loaded drive mechanism and disengage
the Starter. As soon as the Motor Contacts open,
the entire circuit is turned off.
C I R C U I T O P E R A T I O N
CHARGING SYSTEM
The Generator provides voltage to operate
the car's electrical system and to charge its
Battery. A magnetic field is created when cur-
rent 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 elctrical system at
the Battery terminal.
The Generator's regulator uses digital tech-
niques to supply the Rotor current and thereby
control the output voltage. The Rotor current is
proportional to the width of the electrical
pulses supplied it by the Regulator. When the
Ignition Switch is placed in RUN, 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 Gen-
erator 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 digital regulator controls the Charge
Indicator light with a solid state driver. The
driver turns on the light whenever under-
voltage, overvoltage or a stopped generator is
detected.