For Delco Remy CS130 and CS121 Series Alternators, Page
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A basic wiring diagram is shown in Figures 3 and 3A
(above). When operating normally, the indicator bulb will
come on when the switch is turned on, and will then go out
when the engine starts. If the indicator operates abnormally,
or if an under-charged 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 over-night, or by a
defective switch which allows a bulb, such as a trunk or
glove box light, to stay on. This alternator does not have a
regulator by-pass test hole.
Observe the following procedure:
- Visually check belt and wiring and load check battery
- Go to step V. for vehicles without charge indicator
- With ignition switch on and engine stopped, light
should be on. If not, detach harness at alternator, use
fused jumper to ground "L" terminal lead on harness. Be
very carefully to properly identify "L" terminal lead.
Grounding "L" terminal should cause indicator light to
light. If lamp does not light, locate open circuit between
grounding lead and ignition switch. Bulb may be bad.
- Switch on, engine running at moderate speed. Light
should be off. If not, stop engine, turn switch on, and
detach wiring harness at alternator.
- If light goes off, replace or repair
- If light stays on, check for grounded "L" terminal
wire in harness.
- Battery undercharged or over-charged.
- Detach wiring harness connector from
- With switch on, engine not running, connect
voltmeter from ground to "L" terminal in wiring
harness, and to "I" terminal, if used. Wiring harness
may connect to either "L" or "I" or both.
- Zero reading indicates open or grounded circuit
between terminal and battery. Correct as required.
- Re-connect harness connector to alternator, run
engine at moderate speed with all electrical
accessories turned off.
- Measure voltage across battery. If above 16.0,
replace or repair alternator. NOTICE: The alternator
may be O.K. on vehicles using "S" terminal if "S"
terminal wiring has excessive resistance which will
cause high voltage. Refer to vehicle wiring diagram.
Correct wiring as needed, then re-check voltage.
- Connect ammeter at alternator output terminal.
Connect voltmeter across alternator. Turn on
accessories. load battery with carbon pile to obtain
maximum amperes output. Maintain voltage at 13.0 or
- If within 15 amperes of rated output,
alternator is O.K.
- If not within 15 amperes of rated output. Check
belt for slippage or replace or repair