Connect a voltmeter to the positive and negative battery terminals.
Start the engine. During start-up, the voltage can drop to 9.5 volts.
Increase the speed to 3000 rpm. The voltage should be between 13.5 and 14.5 volts. This is proof that the alternator and voltage regulator are functioning properly.
Check regulation stability. To do this, turn on the main beam and repeat the measurement at 3000 rpm. The measured voltage should not drop more than 0.4 volts from the previous measurement.
If the measurement results deviate from the specified values, return the generator to the workshop for verification.