When the engine of your BMW is running, the battery does not bear the bottom-line responsibility for the electricity that needs to be provided to the radio, the lights, and other electronics. That responsibility falls to the BMW alternator. In addition to powering the electronics, the BMW alternator is also responsible for recharging the battery, so that the vehicle may start the next time it is needed to. The unit is attached through a pulley and belt to the crankshaft pulley of the engine. As the engine runs, this belt turns the BMW alternator. The interior housing of this part is lined with a set of strong permanent magnets. In the center of the BMW alternator is a core made of iron, which is then wrapped in copper wires. When the core is turned by the pulley, the copper wires pass through the field of the magnets, and the magnets induce electrons within the copper wires to move. The result is electricity, and this electricity is transferred out of the BMW alternator by small spring arms, called brushes, that ride on the spinning inner core. The electricity produced by the BMW alternator is actually alternating current, which is then converted to the direct current that the vehicle needs with an internal voltage rectifier. When the BMW alternator in your vehicle fails, it is usually due to worn brushes within the unit, or a bad internal rectifier. When you need replacement, you will find the correct version for most vehicles in our large online catalog, at a great price. To order the BMW alternator for you vehicle, visit our secure web site, or place your order by phone, toll-free, at any time of the day or night.