Bosch Alternator for BMW E21 320i M10 1.8L

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The alternator keeps the battery in a constant state of charge anytime the engine is running. If your lights are dimming or you hear excessive bearing noise around the alternator, chances are that it's time for a replacement.

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OEM Bosch Voltage Regulator (Bosch Alternator) - 12311726022 ...

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T#:19326

Part#: 12311726022

In Stock at Vendor

$ 71.99

This product was last offered at the strikethrough price on
01-28-2026

$ 63.99 USD

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$ 63.99 USD

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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. A new set of contacts will be about 13mm in length. Anything less than 5mm and the voltage 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.

The carbon contacts can be replaced on their own but requires desoldering the old ones from the base and then soldering the new ones on. It may be easier to just replace the unit as a whole.

This is the OEM voltage regulator, made by Bosch or Hella. It's the one with the white base and fits most Bosch alternators from 1977-1995 (Valeo and other alternators look very different and have a black cover and base). This part number replaces the previous BMW part numbers - 12311271664, 12321279548, 12311722755, 12321711399 and Bosch part numbers 1197311021 and 1197311028.

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OEM Bosch Starter Relay - E21 320i

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T#:583822

Part#: 61311243207

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$ 4.99 USD

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This is a brand new starter relay from OEM supplier Bosch. If you have replaced your starter and have ruled out every other issue, this relay could restore your starters operation and get your car back up and running.

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Bosch Alternator for BMW E21 320i M10 1.8L

OEM Bosch Voltage Regulator (Bosch Alternator) - 12311726022 ...

OEM Bosch Starter Relay - E21 320i

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