E46Fanatics - View Single Post - BMW E46 Alternator DIY (voltage regulator)
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Old 07-10-2012, 04:12 PM   #107
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Join Date: Jul 2012
Location: San Diego, CA
Posts: 3
My Ride: 2002 325Ci
Ok I just took the regulator out, it was pretty easy. The hardest part was trying to find what size socket to use. Once you get the air box and the power steering reservoir out of the way there is plenty of room.

Originally Posted by tractioncircle View Post
I just replaced my the voltage regulator Bosch 120A on my 02 325i.
Some information on testing the alternator diode pack (Rectifier) that might be useful to someone diagnosing the alternator.

1.> Once you remove the cover from the alternator, you will see six soldered terminals around the back of the alternator. These are obviously the stator windings ends.
2.> To test if your diodes are ok, you need to put your DMM (multimeter) in the diode test mode ( -|>|- ) symbol.
3.> Touch one DMM lead to the soldered winding end and the other to the long bolt (The alternator output, B1+) terminal. This will either give you '1' or some number (I got 436) that is the voltage drop across the diode in mV. Reverse the leads, the readings should be reverse of what you got earlier. i.e. if you got a '1' before, you will get some number now and vice a versa.
4.> Repeat this test with all the six exposed soldered ends. In each case the the reading should reverse. if you get same reading in both directions, You have a failed diode and your alternator will be putting out AC voltage.
5.> Now repeat this test with the smaller bolt coming out of the alternator.
6.> Again repeat this test between the alternator body (ground) and the winding ends. You should get the same results. Same reading in both directions from step 4,5,6 indicating a failed diode inside.


This will tell you if you can get away with just changing the regulator or not.

Thanks Again!
Can anyone clarify this? Especially what the stator winding ends are, I dont see 6 of anything on the back of the alternator, here are the best pictures I could find if someone can point out these winding ends to me


Last edited by yemff; 07-10-2012 at 05:57 PM.
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