IG KEY "OFF", ENGINE "OFF".
Check belt tension which operates alternator .
Check battery terminal and fusible link, poor connection or corrosion of alternator B+ terminal.
Turn Engien "ON.
Operate the electrical device such as head lamp,defroster and blower motor.
Check battery voltage at above 2000 RPM.
Specification : 12.5V~14.5V
Is the measured voltage within the specification?
YES
Alternator is performing within the specification.
NO
Replace alternator and go to "Verification of Vehicle Repair" .