Measure the voltage at the battery when running. It should be 12.4 volts +/- 0.1 volt when engine is off. It should be about 13.5-13.9 volts when engine is running at 1500 RPM
Dunga<br />Agree with the voltmeter. Battery voltage 12.6 volts at 70 degrees. Charging voltage from alternator 13.8 to 14.8 volts from 1000rpms and up.