What is the reason for the car battery light flashing on and off?

[CharlieFitz]

When the car battery indicator light flickers on and off while driving, it may indicate a malfunction. Possible causes: The intermittent illumination of the charging indicator light reflects unstable charging current from the alternator. The potential faulty components mainly include the alternator, voltage regulator, and power supply circuits. If the horn behaves abnormally when the engine speed is high, it suggests that the alternator's output voltage decreases at higher speeds. This could be due to weak alternator brush springs, where increased vibration at higher speeds leads to poor contact and voltage drop. Fault analysis: Excessive wear of the brushes may result in insufficient spring tension, causing poor contact and vibration between the brushes and slip rings, which can lead to slip ring burning. As the slip ring surface becomes rough, the poor contact condition worsens at higher alternator speeds compared to lower speeds. Consequently, the alternator may fail to generate electricity or produce lower voltage at high speeds.