How to determine if the car battery is dead or the alternator is faulty?

When your car won't start or shows electrical problems, it can be difficult to determine whether the issue is a dead battery or a faulty alternator. The key to diagnosis lies in the vehicle's starting and running status.

Signs of a Dead Battery

• Car won't start but lights work dimly
• Clicking sound when turning the key
• Battery is more than 3-5 years old
• Corrosion visible on battery terminals
• Battery case appears swollen

Signs of a Faulty Alternator

• Battery warning light on dashboard
• Dim or flickering headlights while driving
• Electrical accessories malfunction while engine running
• Whining or grinding noise from engine area
• Smell of burning rubber or wires

Simple Diagnostic Test

1. Jump-start the vehicle
2. Remove the jumper cables
3. If the car dies shortly after, the alternator is likely faulty
4. If the car continues running, the battery was simply discharged

Multimeter Testing

• Battery test: Should read 12.4-12.7V with engine off
• Alternator test: Should read 13.8-14.4V with engine running

If you're unsure, it's always best to have a professional mechanic perform a complete electrical system diagnosis to avoid unnecessary part replacements.