Alternator
What it is
The alternator is a belt-driven generator that recharges the battery and powers the car while the engine runs. It is the heart of the charging system.
What it does
It turns engine power into electricity, keeping the battery charged and the electronics fed. A failing alternator causes a dead battery, dimming lights and warning lights — and over- or under-charging can set P0562 (low) or P0563 (high) system-voltage codes.
Symptoms of failure
- Battery / charging warning light
- System-voltage codes P0562 (low) or P0563 (high)
- Dimming or flickering headlights
- Repeatedly dead battery despite a good battery
- Whining or grinding from the alternator
Common fault codes
Which vehicles need it
Every vehicle. The bearings and voltage regulator are the usual failure points.
Replacement cost
| DIY (part only) | $90–$350 |
|---|---|
| At a shop (parts + labor) | $350–$900 |
| Replacement interval | No set interval — often 100,000+ miles; replace on failure. |
| DIY difficulty | Moderate (DIY) — belt and a few bolts; access varies by engine |
| Recommended brands | Bosch, Denso, Valeo, ACDelco |
Where to buy the part
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Frequently asked questions
Is it the battery or the alternator?
A quick test: with the engine running, system voltage should be about 13.5–14.5 V. If it is low (near 12 V) the alternator is not charging; if the car will not crank but charging is fine, suspect the battery. A P0562/P0563 code helps pinpoint it.
Can I drive with a failing alternator?
Only briefly. Once the alternator stops charging, the car runs off the battery and will stall when it drains — often within minutes to an hour. Fix it before driving far.