Alternator Failure
Alternator Failure
Section titled “Alternator Failure”The alternator charges the battery and powers electrical systems. E46 alternators typically last 100,000-150,000 miles.
Symptoms
Section titled “Symptoms”- Battery warning light on dashboard
- Dimming headlights
- Electrical accessories malfunctioning
- Difficulty starting
- Battery not holding charge
- Whining noise from alternator
Diagnosis
Section titled “Diagnosis”- Check charging voltage: Should be 13.8-14.4V with engine running
- Load test alternator output
- Check belt tension and condition
- Inspect alternator connections for corrosion
Replacement
Section titled “Replacement”The alternator is located on the front of the engine, driven by the serpentine belt. Part: 12 31 7 515 030 (120A)