1. Make sure the alternator drive belt is normal.
If the above steps do not produce results, we recommend that you have the generator checked by a workshop. If further troubleshooting is carried out independently, then special care and attention are required to avoid mixing up the terminals when connecting the measuring device. In this case, complete damage to the generator cannot be ruled out.
2. Connect a voltmeter to both battery terminals and start the engine.
3. Increase engine speed and simultaneously monitor the voltmeter readings. As soon as the voltmeter shows a voltage in the range of 13.5-14.8 V, leave the engine running at the speed at which this voltage is shown and turn on the maximum possible number of on-board network consumers. The battery voltage must remain within the specified values. If it changes, then most likely the voltage regulator is faulty or the generator brushes are worn out. If the voltmeter registers too high a battery voltage, then the rectifier diodes have burned out.
(Information copied from the resource: peugeotbook)
If the inspection reveals that the generator is faulty, it can be removed and taken to a workshop for repair. We do not recommend repairing the generator or voltage regulator yourself unless you have sufficient experience. If such a service is offered, the workshop can exchange the removed generator for a repaired one of the same model. Minor generator repairs, such as replacing carbon brushes, can be performed at an electrical repair shop.
The generator is equipped with bearings that are lubricated for their entire service life and therefore do not require maintenance. The outer surface of the generator housing should be kept clean and free from water or solvents.
Carbon brushes operate on slip rings and therefore have a fairly long service life. If you suspect that the carbon brushes may be the cause of the generator's power loss, it is recommended to contact an electrical repair shop.