What are the symptoms of a faulty alternator carbon brush in a car?

[FranciscoDella]

When the alternator carbon brush in a car is faulty, it can cause symptoms such as the starter not turning or turning weakly, and the inability to generate electricity. A carbon brush motor can last up to 2000 hours under good commutation conditions, but under extreme conditions, it might only last 1000 hours. Generally, carbon brush motors can have a lifespan ranging from 1000 to 3000 hours. The reasons for carbon brush sparking in the alternator include: 1. Dirty surfaces on the slip ring, carbon brush, brush holder, and brush frame; 2. Sticking edges of the brush holder and uneven spring pressure; 3. Significant vibration in the unit's shaft system, causing the slip ring to vibrate as well; 4. Poor contact of the carbon brush, leading to increased contact resistance and uneven current distribution among the carbon brushes, resulting in sparking.