Alternator, how it works, symptoms, testing, problems, replacement
Alternator. Click for larger photo
An alternator is a generator of electric power in you car and is a major component of your vehicle's charging system. Whenever your engine is running, the alternator charges your battery and supplies additional electric power for the vehicle's electrical systems. An alternator is attached to the engine and is driven by a drive belt (also known as a serpentine belt).
An alternator is a maintenance-free unit. On average, an alternator can last for 8-12 years without any repairs. If an alternator fails, the car may still run on battery power alone for a short time, but will die as soon as the battery charge is depleted. Replacing an alternator with a new unit is quite expensive, but there are alternatives. Read more below.
Battery-shaped warning light indicates a problem with a charging system
The most frequent 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 the ignition, but should disappears 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. You mechanic will need to do further testing to pinpoint the defective part.
Sometimes when the alternator becomes weak, you may notice that your car's headlights and dash lights become dim at idle, but get brighter at higher RPMs.
How an alternator is tested
Should an alternator be replaced or rebuilt? What is cheaper? Read Next.
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