ALTERNATOR EXPLAINED
An alternator is a generator of electric power in a car and is a major component of the vehicle's charging system. All cars with an internal combustion engine except for some hybrids have an alternator. When an engine is running, the alternator charges the battery and supplies additional electric power for the vehicle's electrical systems. An alternator is bolted to the engine and is driven by a serpentine belt (drive belt).
An alternator is a maintenance-free unit. In some cars, it can last for up to 10-15 years without any repairs. If an alternator fails, the car may still run for a short time on battery power. However, the engine will stall as soon as the battery charge is depleted. Replacing an alternator with a new OEM part is expensive, but there are alternatives. Read more below.
Symptoms of alternator problems
The most common symptom of a problem with your vehicle's charging system is a battery-shaped warning light (in the photo) or the "CHARGE" icon that comes on while driving. Normally this warning light should come on when you turn on the ignition, but should disappear as soon as the engine is started. If it stays on, there is a problem with your charging system. The charging system warning light doesn't point directly to a failed alternator, although alternator problems are very common. Your mechanic will need to do further testing to pinpoint the defective part.
Another symptom of a weak charging system is when the dash lights and headlights dim at idle, but become brighter when the engine is revved. This problem could be caused not only by a weak alternator, but also by a failing battery, poor connection at the battery terminals or a loose serpentine belt. A whining/buzzing noise coming from the alternator is another symptom of alternator troubles. In some cars, it could be caused by a noisy alternator bearing. In some Jeep/Chrysler vehicles, a bad alternator decoupler pulley could cause the same noise.
