Voltage Regulator (Bosch Alternator) - 12311747920 - E34,E36,E36 M3
This is the voltage regulator found on the back of the alternator. It's a normal wear item and the contacts are the first thing to check if you believe the alternator is not charging the battery (lights flickering or dim, battery light on in the dash, the engine quits without warning, or other electrical failures). The voltage regulator manages the voltage flowing through the car, especially to and from the battery. There are two carbon contacts on the regulator that control the magnetic field when the alternator is spinning and these contacts wear over time. There is a wear mark on the contacts and if the tip is within 3mm of this wear mark the regulator should be replaced, regardless if that is the cause of your electrical problems or not. Most older mechanics will tell you to keep a spare regulator in your toolbox.
Bosch is one of the largest OEM producers of Genuine BMW and aftermarket parts in the world, providing parts for almost every major automotive manufacturer. Bosch has likely supplied many of the original electrical (and mechanical) parts for your BMW. Thanks to their exacting assembly process and high level of durability you can expect a long service life from all Bosch products.
This is the OEM Bosch voltage regulator and will only fit Bosch alternators.
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