Ford 2003 Mustang Workshop Manual page 3346

SECTION 414-00: Charging System — General Information
DESCRIPTION AND OPERATION
Charging System
The charging system is a negative ground system consisting of the following:
generator
internal voltage regulator
charging system warning indicator
storage battery
necessary wiring and cables
The generator is belt-driven by the engine accessory drive system.
With the ignition key in the run position, voltage is applied through the warning indicator I circuit to the
voltage regulator. This turns the regulator on, allowing current to flow from battery sense A circuit to
the generator field coil. When the engine is started, the generator begins to generate alternating
current (AC) which is converted to direct current (DC) internally. This current is then supplied to the
vehicle's electrical system through the output terminal (B+) of the generator.
Once the generator begins generating current, a voltage signal is taken from the generator stator and
fed back to the internal regulator. This voltage feedback signal (typically half the battery voltage) is
used to turn off the warning indicator.
With the system functioning normally, the generator output current is determined by the voltage of the
A circuit. This A circuit voltage (battery sense circuit) is compared to a set voltage internal to the
regulator, and the regulator controls the generator field current to maintain the correct generator
output.
The set voltage will vary with temperature and is typically higher in cold temperatures than in warm
temperatures. This allows for better battery recharge in the winter and reduces the chance of
overcharging in the summer.
The battery is a 12 volt direct current source connected in a negative ground system. The battery case
is sealed and includes two vent holes to release gases. The battery has three major functions:
engine cranking power source
voltage stabilizer for the electrical system
temporary power when electrical loads exceed the generator output current
Circuit Description
Battery Output Terminal (B+)
The generator output is supplied through the battery positive output (B+) terminal on the back of the
generator to the battery and electrical system.
I Circuit 904 (LG/RD)
The I (ignition) circuit is used to turn on the voltage regulator. This circuit is powered up with the
ignition key in the run position. This circuit is also used to turn the charging system warning indicator
on if there is a fault in the charging system operation.
2003 Mustang Workshop Manual