E46Fanatics - View Single Post - BMW E46 Alternator DIY (voltage regulator)
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Old 10-09-2012, 03:38 PM   #109
Registered User
Join Date: Oct 2012
Location: Georgia
Posts: 1
My Ride: 2003 330CIC
Thanks E46 Fanatics! and adding my E46 Alternator Repair Comments

Thanks for the posts about alternator repair. It was a huge help to me! I thought I would return the favor and post my experience.

I have a 2003 330CIC. I had just replaced the battery and the dash light indicating "no charge" came on. After checking the E46 Fanatic posts, I figured either the alternator or volatage regulator was crapped out. Checking the battery with the car running indicated ~11.5 VDC....nothing at all was coming from the alternator!

I followed the other posts guidance and had the alternator out in no time. I do think it is easier to pull the fan assembly, both belts, air cleaner box, and leave the power steering reservoir in place. The only real headache was the bottom bolt with the "sliding nut" that was very frozen in place. You can see this nut in the pix (a captured rusty look nut). A pry bar was needed to free it. Be sure before re-assembly to tap this nut out a little with a piece of brass or something so as to gain some clearance when putting the alternator back in place.

Anyway, after getting the alternator out, the bearings sounded fine when hand spinning and the collector rings looked OK (not great but OK)...see pix. The alternator also passed the "smell test". If the windings get hot, the varnish burns off and has a distinct "electrical" smell.

A quick check of the diodes indicated they were fine. Although not comprehensive, you can check them with the diode setting on your DVM. Remember there are two sets of diodes (forming the full wave rectifier), see my crude drawing also in the pix. Three diodes are between the common ring to ground and the other three are between the common ring and the battery. The common ring is the "bent piece of heavy wire" connecting all the diode pins. All (when forward biased) are facing the battery. Again, with your DVM set on "diode check", check across the common ring and the diode, when forward biased they should be reading ~.4 VDC and when reversed biased they should read "open" or "OL". Change the bias by changing the position of your test leads. Red to black, forward biased and vice versa. Again, see pix.

If the bearings look good and the diodes check out, it is likely the VR. I ordered mine from Autohausaz.com for $42 and some change (Bosch OEM). Even after shipping, I was under $50!

After getting everything back together, I had 13.4 VDC on the battery when running. Life was good and the beemer was back on the road.

Again, thanks to all that posted and I hope mine will help someone a little!
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