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Old 06-13-2008, 02:39 PM   #1
Registered User
Join Date: Jan 2008
Location: Chicago
Posts: 61
My Ride: 330Ci Sold
BMW E46 Alternator DIY (voltage regulator)

Hello everyone,

I saved so much money working on my BMW and all thanks to e46fantatics! Thank you everyone for posting! I feel that I have to give something back to the community. So here is my first diy guide.

I searched this site, google, could not find how to change voltage regulator and brushes on e46. Decided to do it myself.

Initial problem was that alternator would give only ~10.3V if I had my lights and AC on. That drained my new battery. As my car is 2001 (06/2000 production), I decided that it was either brushes or voltage regulator. Ordered Voltage regulator (it comes with brushes) from pelicanparts, it is $53 (compared to $212+shipping on re manufactured Bosch alternator).

There is a good guide how to replace the alternator


so I won't repeat it. When you have your alternator out, there is a plastic back plate. You have to remove one screw (#3 in picture and two nuts (#1 an #2). #1 is under this rubbery plastic cover, use screw driver to pry it out.

- The nut holding down the positive cable is 17mm
- #3 is a Philips screw
- #1 and 2 are 15mm nuts (deep wall socket is most likely needed)

After you remove the cover, you should find ..... this

I found all sort of stuff - leaves, paper, cigarette butts, you name it. The voltage regulator is connected with 3 screws and slides out after, no clips.
My old brushes were worn, but not to the extent that alternator would not work, one was shorter than the other one. Go figure...

The whole process takes about 10-15 minutes (after you have alternator out). It is cheaper that buying refurbished alternator and it is way cheaper than taking to the dealership. If you alternator does not make any noises (ball bearings) changing just the regulator will save you lots of money. I believe it is easier to do this than remove the pulley while switching alternators... After I changed the regulator, with long beams on, AC on it runs 13.6V to my battery, I believe that is within specs of 13.5 -14.5V. Maybe on the lower side, but hey, its not 10.3V like before.

I hope that helps someone.

Part number from pelikan $53 12-31-7-559-183-M14 link
2001 330CI

Last edited by Solidjake; 04-10-2013 at 08:22 PM. Reason: Auto-save 1365643347
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