Alternator Failure
If the battery light comes on, lights dim or the car stalls while driving, the alternator may not be charging.
Can I drive it? Drive with care
You can drive only as far as the battery lasts, often 10-30 minutes with electrics off. Head straight to a shop or safe place.
Typical repair cost
$400-$900 for an alternator (parts and labour), $100-$250 for a belt.
General US estimates, not quotes. Prices vary by region, vehicle and shop.
Symptoms to Look For
These signs indicate you might be experiencing this issue
- Battery warning light on dashboard
- Dim or flickering lights
- Engine stalling or dying while driving
- Whining noise from engine belt area
Potential Causes
Most likely reasons for this problem, sorted by probability
Repair Solutions
Step-by-step instructions to diagnose and fix the problem
1Check Voltage Output
- 1
Use a multimeter on battery terminals while engine is running
- 2
Voltage should be between 13.5V and 14.5V
- 3
If below 13V, the alternator is likely not charging
Need professional help?
Find a repair shop near you, or describe your exact symptoms to the AI mechanic
When to See a Mechanic
Do not wait if any of these apply
- The battery light is on while driving
- The car dies while driving
- A whining noise from the front of the engine
How to Prevent It
Simple habits that stop this problem coming back
- Replace the serpentine belt at the interval in your manual
- Keep the battery healthy; a weak one strains the alternator
- Do not repeatedly jump-start to charge a dead battery
Frequently Asked Questions
Can a bad alternator drain a new battery?
Yes. A failing alternator does not charge, so even a new battery runs flat.
How far can I drive on a failed alternator?
Only until the battery is drained, often 10-30 minutes with lights, HVAC and radio off.
Related Issues
AI-generated and informational only. This is not a diagnosis of your specific vehicle and does not replace inspection by a qualified technician.