Service Manual User Manual

Section 10
10-42
Model 3606 • Origin 10/99
10.7 CHARGING CIRCUIT
The charging circuit consists of the battery and a belt-
driven alternator with an internal voltage regulator. These
components work together to provide electrical power for
the vehicle, including the starting system, operators dis-
play panel, horn, solenoids, back-up alarm, joystick, logic
panel and all accessories. Examine the appropriate wir-
ing diagrams and schematics earlier in this section to
understand the wiring circuits involved.
Current flows from the positive post of the battery to the
BATT terminal on the starter motor.
When the ignition switch is in the RUN position, current
flows from the instrument cluster terminal to the alterna-
tor D+ terminal, and is used to excite the field windings
and the alternator begins emitting a charge. Current
flows from the alternator B+ terminal to the starter motor
B terminal, then through the positive (+) battery cable to
the battery. The circuit in the instrument panel connects
to the battery positive terminal through the fuse panel
and detects field voltages in excess of 16 volts or system
voltages less than 2 to 4 volts less than battery voltage.
Either of these conditions will cause the warning light in
the operators display panel to illuminate.
The warning indicator (A, Fig. 10– 32), a battery-shaped
icon on the operators display panel, illuminates for three
seconds when the engine is started and will remain illu-
minated if the engine is not running. The warning indica-
tor illuminates when the battery is at a low state of
charge, and when the alternator is no longer able to
charge the battery.
Figure 10– 32. The battery warning indicator (A) is located
on the operators display panel.
The negative (-) post of the battery is connected to the
main chassis ground, a stud located on a triangular weld-
ment at the hydraulic reservoir. Other ground leads
routed directly from the main chassis ground are pro-
vided to the alternator, fuel shutoff switch, maintenance
reset switch and spliced within the wiring harness to
other electrical system grounds.
The alternator includes an internal voltage regulator that
limits alternator voltage to a pre-set value and helps pre-
vent circuit overloads, power surges, etc. during peak-
voltage output.
Beyond inspecting the fan belt every 1,000 hours of
engine operation, there is no periodic maintenance
required for the charging circuit. When inspecting the fan
belt, also check the electrical wiring and connectors.
Under normal conditions the alternator will have no prob-
lem keeping the battery charged. The only condition in
which the battery may cause a problem is when it has
been completely discharged for an extended period of
time. In this condition, the alternator may be unable to
recharge the battery, and a battery charger will be
required for recharging.
Before using a battery charger, an attempt can be made
to recharge the battery by jump starting the vehicle (refer
to
Section 2.12.15 Battery
, sub-paragraph
C. Jump Start-
ing
). Allow the engine to run, which enables the alterna-
tor to charge the battery.
If the alternator charging warning indicator illuminates,
perform the following checks:
1. Check the battery cable connections at the battery
and verify that they are clean and tight.
2. Check the external alternator wiring and connections
and verify that they are in good condition.
3. Check the fan belt condition and tension (refer to
Section 2.12.8 Engine Fan Belt
).
4. Verify that the alternator mounting hardware is tight.
5. Run the engine and check the alternator for noise. A
loose drive pulley, loose mounting hardware, worn or
dirty internal alternator bearings, a defective stator or
defective diodes can cause noise. Replace a worn or
defective alternator.
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MS0540
WARNING: DO NOT charge a frozen battery.
A frozen battery may explode and cause seri-
ous personal injury. Allow the battery to thaw
before “jump starting” the vehicle or connecting
a battery charger.