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The alternator, which is bolted to the engine, keeps your car’s battery charged and produces the electrical power necessary to run the vehicle’s electrical systems. When starting your car, stored energy in the battery powers the starter motor. Once the engine is running, the alternator produces the electrical energy that your car needs by spinning a magnet on a rotor through a stationary coil of wire. To ensure that the alternator provides the right voltage output for your car’s electrical system, there is a voltage regulator built into the alternator. The voltage regulation is built into the car’s Powertrain Control Module (PCM) on newer vehicles.
The following electrical or mechanical faults are signs that the alternator may need to be replaced:
One should exercise caution. Should the alternator fail while you are driving, the battery alone will power the car’s electrical system for a short while. Cars require a substantial amount of electrical power though and the battery will likely discharge relatively quickly. The car may stall and it would be impossible to re-start if the battery discharged completely. When the battery or charging system warning light illuminates, the situation should be investigated and resolved as soon as possible.