The alternator generates electrical power while the engine runs — recharging the battery and powering every electronic accessory.
A serpentine-belt-driven rotor spins inside a fixed stator, producing AC current. A built-in rectifier converts it to ~14V DC and a voltage regulator holds it steady regardless of RPM or load.
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Replacement runs $250–$850 including parts and 1-3 hours labor. Exact cost depends on vehicle, parts tier (OEM vs aftermarket), and local labor rate.
Expected lifespan is 80,000-150,000 miles or 7-10 years. Driving conditions, climate, and maintenance affect real-world life.
Battery warning light; Dim or flickering headlights; Slow-cranking starter; Burning rubber smell from worn belt; Whining or grinding noise; Dead battery (frequently jumped).
Most modern alternators are sealed units that get replaced rather than rebuilt. A shop will diagnose, confirm with a load or output test, then swap the unit and verify operation.
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