1. If the alternator is not charging the battery, check the condition of its drive belt and its tension. Check the reliability of the fastening of the wires of the generator and battery.
2. To accurately measure the output current of the generator, special equipment is required. Approximately, it can be estimated using a voltmeter for 0-15 V or 0-20 V as follows.
3. Connect a voltmeter to the battery terminals. Turn on the headlights and notice the voltmeter readings: the voltage should be 12-13 V.
4. Start the engine and leave it running at fast idle (approximately 1500 rpm). The voltmeter should show 13-14 V.
5. With the engine still running at fast idle, turn on as many electrical loads as possible (rear window defroster, interior heater blower, etc.). The voltmeter should still show 13-14 volts. If necessary, you can slightly increase the speed of the engine so that the voltage does not drop.
6. If the generator does not charge the battery well or does not charge it at all, inspect the brushes. If they are in order, you should contact a specialist.
7. It is possible that the generator gives too high current. A sign of this is constantly burning out lamps, a noticeable change in the brightness of the glow of the lamps depending on the speed of the engine, overheating of the generator or battery, the release of steam or smoke from the battery. The reason for this is almost certainly a faulty voltage regulator, but in this case, the intervention of a specialist is also necessary.