I am going to try some of this our right now......................
Ensure drive belt tension is correct.
Check battery for loose or corroded connections and loose battery posts.
Remove battery hold down clamps and shields, then inspect for broken or cracked case or cover.
Ensure battery drain is less than 50 milliamps and battery is at capacity.
Measure voltage at "B+" terminal on back of alternator. If battery voltage is present, proceed to step 6. If less than battery voltage, repair open in "B+" circuit.
Measure voltage at voltage regulator test point "A." If battery voltage is present, proceed to step 7. If less than battery voltage, repair fuse or open in circuit between alternator "A" and power distribution box.
Measure voltage at voltage regulator test point "F." If battery voltage is present, proceed to step 8. If less than battery voltage, proceed to step 14.
Turn ignition switch to RUN and measure voltage at wiring harness terminal "I." If voltage is greater than one volt, proceed to step 9. If voltage is less than one volt, repair open or high resistance in circuit between alternator "I" and battery warning indicator.
Measure voltage drop between voltage regulator test point "A" and positive battery post. If drop is less than 0.25 volt, proceed to step 10. If drop is more than 0.25 volt, service circuit between alternator terminal "A" and power distribution box. Ensure fuse and connectors are in good condition.
Measure voltage at voltage regulator test point "F." If less than two volts, proceed to step 11. If more than two volts, proceed to step 14.
Remove one pin "S" connector from alternator. Measure voltage between "S" terminal and ground, then between "S" terminal and positive battery terminal. If voltage is less than one volt at both terminals, proceed to step 12. If voltage is more than one volt at either terminal, replace alternator.
Install "S" connector, start engine, turn headlamps ON and set blower speed to HIGH. With engine running at 2000 rpm, measure voltage drop between "B+" terminal of alternator and positive battery post. If voltage drop is less than 0.5 volt, proceed to step 13. If voltage drop is more than 0.5 volt, service "B+" circuit. Ensure fuse and connections are in good condition.
Use a jumper wire to connect voltage regulator test point "F" to negative battery post, then measure alternator output amperage at 2000 RPM. If output amperage is more than alternator rating, replace regulator. If rating is less than specified, refer to Output Test. See: In-Vehicle Testing\Output Test
Remove alternator, then the voltage regulator.
Measure resistance between alternator slip rings.
If resistance is 1-10 ohms, inspect for worn brushes or open brush leads. Replace as required.
If brushes are in good condition, replace voltage regulator.
