Undercharged Battery

1. Ensure undercharged condition has not been caused by accessories left on for extended periods.
2. Check drive belt for proper tension.
3. Inspect wiring for defects. Ensure all connections are clean and tight, including slip connectors at alternator and bulkhead. Also, check battery cable connections at battery, starter and ignition ground cable.

Fig. 2 Alternator Output Measurement:

4. Connect a suitable voltmeter and ammeter as shown, Fig. 2. Connect voltmeter between alternator B terminal and ground. Connect ammeter between alternator B terminal and battery positive terminal.
5. Perform no-load check as follows:
a. Increase engine speed from idle to 2000 RPM and note readings. Voltage readings will vary with regulator case temperature.
b. If voltage is higher than 14.2-14.8 volts at 77°F, replace IC regulator.

Fig. 4 Grounding Terminal F:

c. If voltage is below specification, check IC regulator and alternator by measuring voltage at B terminal while grounding F terminal, Fig. 4. If voltage is above specification, replace IC regulator.
d. If voltage is below specification, perform load check.
6. Perform load check as follows:
a. Run engine at 2000 RPM and switch on headlights and heater blower motor.
b. Ensure current is at least 20 amps, if less, alternator is defective.