Cs-130 Charging System - GMC G Service Manual

GENERATOR DIAGNOSTIC TESTER INDICATIONS
If a tester is available, check the generator following the
tester manufacturer's instructions. It will indicate about 98
percent of the charging system problems.
TRANSISTORIZED VOLTAGE REGULATOR TEST
Connect a fast charger and a voltmeter to the battery as
shown in figure 16. With the engine control switch on "RUN"
and the engine "OFF," slowly increase the charge rate. The
charging system indicator lamp (on vehicles without gages)
will dim at the voltage regulator setting. The setting should
be at a minimum of 13.5 volts and a maximum of 16.0 volts.
This test works if the rotor circuit is good, even if the
stator, rectifier bridge or diode trio are bad.
74. Fast Charger
75. Voltmeter
66. Battery
Figure 16 — On-Vehicle Regulator Test

CS-130 CHARGING SYSTEM

CIRCUIT DIAGNOSIS
Trouble in the charging system will show up as one or
more of the following conditions:
• Abnormal operation of indicator lamp.
• An undercharged battery as evidenced by slow
cranking or dark hydrometer.
• An overcharged battery as evidenced by excessive
spewing of electrolyte from the vents.
A basic wiring diagram for the charging system is shown
in figure 12. When the system is operating normally, the
indicator lamp (on vehicles so equipped) will come on when
the engine control switch is turned on and go out when the
ENGINE ELECTRICAL 6P-13
engine starts. If the lamp operates abnormally, or if an
undercharged or overcharged battery condition occurs, the
following procedure may be used to diagnose the charging
system. Remember that an undercharged battery is often
caused by accessories being left on overnight, or by a
switch stuck closed which allows a lamp, such as a trunk or
glove box lamp, to stay on.
This generator does not have a field ground hole.
DIAGNOSTIC TEST FOR CS-130
1. Check belt for wear and tension. Refer to ENGINE
COOLING (SEC. 6B1) for belt tension. Check wiring.
2. Go to Step 5 for vehicles without a charge indicator
lamp.
3. With the engine control switch "ON" and the engine
stopped, the lamp should be "ON." If not, detach the
wiring harness at the generator and ground the "L"
terminal lead.
• If the lamp lights, replace the generator.
• If the lamp does not light, locate the open circuit
between the grounding lead and the engine
control switch. The lamp may be open.
4. With the switch "ON" and the engine running at mod­
erate speed, the lamp should be "OFF." If not, detach
the wiring harness at the generator.
• If the lamp goes out, replace the generator.
• If the lamp stays on, check for a grounded "L"
terminal wire in the harness.
5. If the battery is undercharged or overcharged:
• Detach the wiring harness connector from the
generator.
• With the switch "ON" and the engine not run­
ning, connect a voltmeter from ground to the "L"
terminal in the wiring harness, and to the "I"
terminal, if used. The wiring harness may con­
nect to either "I" or to both.
• A zero reading indicates an open circuit
between the terminal and the battery. Correct
as required.
Connect the harness connector to the generator
and run the engine at moderate speed with
accessories "OFF."
• Measure the voltage across the battery. If
above 16 volts, replace the generator.
• Connect an ammeter at the generator output
terminal, turn on the accessories and load the
battery with a carbon pile to obtain maximum
amperage. Maintain voltage at 13 volts or
above.
• If the output is within 15 amperes of the
rated output, the generator is OK. Refer to
"Specifications" at the end of this section.
• If the output is not within 15 amperes of
the rated output, replace the generator.