Alternators provide electricity to power a vehicle's accessories, such as lights and radio, and charge its battery. It converts the mechanical energy created by the crankshaft in the engine into electrical energy via induction. The energy-conversion process creates a magnetic field, which then charges the wires that connect the alternator to the battery and accessories.
There are four signs that an alternator may be failing. The most obvious sign is the warning light on the dashboard that turns on to indicate a problem with the alternator. This light may be shaped like a battery or say "ALT" or "GEN." The warning light is connected to the vehicle's electrical or computer system, which monitors the level of voltage being generated by the alternator. If the output voltage falls below a certain level, the battery cannot recharge and the vehicle may stall and require a jump to restart. If the battery continues to die when the vehicle is in motion, or the vehicle does not start after being parked, the alternator may be damaged, especially if the battery is relatively new. Other signs of a failed alternator include dimming headlights and a growling or whining sound, sometimes accompanied by the smell of burned rubber.