ENGINE ELECTRICAL 2-9
CHARGING SYSTEMGeneral Information
The charging system is a negative (-) ground system which consists
of an alternator, a regulator, a charge indicator lamp, a storage battery,
circuit protection and wiring connecting the components.
The alternator is belt-driven from the engine. Energy is supplied from
the alternator (with integral regulator) to the rotating field through
brushes to slip-rings. The slip-rings are mounted on the rotor shaft and
are connected to the field coil. This energy supplied to the rotating field
from the battery is called excitation current and is used to initially ener-
gize the field to begin the generation of electricity. Once the alternator
starts to generate electricity, the excitation current comes from its own
output rather than the battery.
The alternator produces power in the form of alternating current. The
alternating current is rectified by diodes into direct current. The direct
current is used to charge the battery and power the rest of the electrical
system. When the ignition key is turned on, current flows from the bat-
tery, through the charging system indicator light on the instrument
panel, to the voltage regulator, and to the alternator. Since the alternator
is not producing any current, the alternator warning light comes on.
When the engine is started, the alternator begins to produce current and
turns the alternator light off.
As the alternator turns and produces current, the current is divided in
two ways: charging the battery and powering the electrical components
of the vehicle. Part of the current is returned to the alternator to enable it
to increase its output. In this situation, the alternator is receiving current
from the battery and from itself. A voltage regulator is wired into the
current supply to the alternator to prevent it from receiving too much
current, which would cause it to overproduce current. Conversely, if the
voltage regulator does not allow the alternator to receive enough current,
the battery will not be fully charged and will eventually go dead.
The battery is connected to the alternator at all times, whether the
ignition key is turned on or off. If the battery were shorted to ground, the
alternator would also be shorted. This would damage the alternator. To
prevent this, circuit protection (usually in the form of a fuse link) is
installed in the wiring between the battery and the alternator. If the bat-
tery is shorted, the circuit protection will protect the alternator.
Alternator Precautions
To prevent damage to the alternator and regulator, the following pre-
cautionary measures must be taken when working with the electrical
system.
- Never reverse the battery connections. Always check the battery
polarity visually. This is to be done before any connections are made to
ensure that all of the connections correspond to the battery ground polarity
of the car. - Booster batteries must be connected properly. Make sure the posi-
tive cable of the booster battery is connected to the positive terminal of the
battery which is getting the boost. - Disconnect the battery cables before using a fast charger; the
charger has a tendency to force current through the diodes in the opposite
direction for which they were designed. - Never use a fast charger as a booster for starting the car.
- Never disconnect the voltage regulator while the engine is running,
unless as noted for testing purposes. - Do not ground the alternator output terminal.
- Do not operate the alternator on an open circuit with the field ener-
gized. - Do not attempt to polarize the alternator.
- Disconnect the battery cables and remove the alternator before
using an electric arc welder on the car. - Protect the alternator from excessive moisture. If the engine is to be
steam cleaned, cover or remove the alternator.
Alternator
TESTING» See Figure 29
A voltmeter and ammeter are necessary for testing.- Make sure the battery terminals are not loose or corroded. Check the
fusible link for continuity. - Inspect the drive belt for excessive wear. Check the drive belt tension.
If necessary adjust the drive belt.
Ammeter
Disconnect Wire
from Terminal BBattery
Generator
Fig. 29 Alternator, voltmeter and ammeter test connections- Check the following fuses for continuity: ENGINE, CHARGE, IGN
fuses. - Visually check alternator wiring and listen for abnormal noises.
- Check that the discharge warning light comes ON when the ignition
switch is turned ON. Start the engine. Check that the warning light goes out. - Check the charging circuit WITHOUT A LOAD.
a. Disconnect the wire from terminal B of the alternator and attach it
to the negative lead of the ammeter.
b. Connect the positive lead of the ammeter to terminal B of the alter-
nator.
c. Connect the positive lead of the voltmeter to terminal B of the
alternator.
d. Ground the negative lead of the voltmeter.
e. To check the charging circuit, run the engine from idle to 2000
rpms and check the reading on the ammeter and voltmeter. Standard
amperage is 10 amps or less. Standard voltage is as follows:
- 77°F(25°C)—14.0-15.0 volts
- 239°F(115°C)—13.5-14.3 volts