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Old 01-20-2014, 02:23 PM   #131
hitbyastick
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Join Date: Sep 2013
Location: DC
Posts: 895
My Ride: 2002 325i
I've read this thread and unless I missed it, nobody here seems to be paying any attention to the slip rings on their alternators as they opt to replace the voltage regulators. I had mine out for a look last time I was in the engine doing something (OFHG) and removed the VR. I noticed the slip rings had deep grooves worn into them from spinning against the brushes.

Replacing the voltage regulator is pointless in this scenario. You need to rebuild the alternator in this case. I can't imagine mine at 125k being much different than anyone else's at 125k. Anything can happen though.

Voltage regulators are over $100 for the Valeo. The cost of all the rebuild parts for the alternator including bearings, slip rings, and new voltage regulators would substantially exceed the cost of a rebuilt alternator, and perhaps be on par with that cost if you just replaced the brushes in the voltage regulator rather than the entire thing. Rebuilt alternators cost $150 after you send in the core.

Rebuilding an alternator yourself is entirely doable. Procuring quality bearings and the correct slip rings & voltage reg/brushes can be a pain, since it doesn't seem possible to just buy it all from one place. The parts must be sourced from at least two different vendors. So you will spend some real time here doing research and procuring parts. Then you need to disassemble the alternator. Getting the bearings in and out require bearing pullers/presses. Replacing the slip ring is a job, have to dig the epoxy from the winding joints, and be careful doing it because you can render your core useless if you hamfist it. And then you have the brushes in the VR which is another fiddly but easy job. Even though I am entirely competent enough to rebuild the unit no problem, there comes a point when saving money yields a diminished return.

To me the choice is obvious. It's not just the voltage regulator that wears out, it's not just the brushes, or the bearings. Unless you are determined to save as much money as you can and you don't care how much fiddling you have to endure to do it, just buy a whole rebuilt alternator and be done with it.
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