How to Diagnose a Car Alternator Failure?

1. Check for a lit battery warning light on the dashboard.

2. Test battery voltage with a multimeter (engine off and running).

3. Listen for unusual noises (grinding, whining) near the alternator.

4. Inspect the drive belt for wear, cracks, or improper tension.

5. Look for corrosion on alternator terminals and wiring.

6. Perform a "voltage drop test" on charging system cables.

7. Check alternator output under load (headlights, AC on).

8. Test diodes for AC ripple using a multimeter.

9. Examine the alternator pulley for free spin or binding.

10. Swap with a known-good unit or bench-test for confirmation.

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