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-   -   Preventative replacement of alternator? (https://xoutpost.com/bmw-sav-forums/x5-e70-forum/116454-preventative-replacement-alternator.html)

80stech 12-03-2025 09:02 AM

Quote:

Originally Posted by Bdc101 (Post 1247575)
Mine was a Bosch rebuilt unit that failed prematurely, not a new one. Bosch "rebuilt" units are done by some chinese third party under license. The second time I replace it, it was easy to spend a few extra bucks for a Valeo.

Yep, the way things change these days with companies it's a crap shoot! ;)
When I bought a Bosch rebuilt it was more expensive than the new Bosch but turned out to be good.

andrewwynn 12-03-2025 09:33 AM

It's a dice throw. That said alternator swap on m54 is about 3/10 difficulty sou recommend getting whichever didn't raise your Spidey sense but get it from a big national brand with stores within a bike ride distance and a lifetime warranty.


–awr–

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Bdc101 12-03-2025 03:05 PM

I just checked and Valeo is the original manufacturer for the 220-amp alternator on my 35d (according to RealOEM).


Part number 12317603775 is the voltage regulator and is only about $60 for a Valeo version. Andrew, do you know if I need any special tools to remove the voltage regulator? The last time I did this was on a Toyota about 15 years ago and it was just attached to the end of the alternator. But FCP has a bunch of "decoupler" tools in their section for the alternator. Just want to check before I take the car apart.


Edit: Nevermind, it appears you can access it on the back of the alternator if you take it off.

andrewwynn 12-04-2025 01:55 AM

I have a write up on xoutpost that shows how I actually refurbished mine and I’m pretty sure it shows the process of removing and reinstalling.

it was quite a while ago. I can’t remember if soldering was involved. I of course, did Saturn because I switched the polarity of the field winding.


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josiahg52 02-05-2026 07:23 PM

My 190k alternator died yesterday afternoon. Got a cheap Duralast in there to get me on the road but I'm rebuilding my original alternator and replacing the overrun pulley along with all of the other front accessory drive components including a Fluidampr unit.

andrewwynn 02-05-2026 07:38 PM

Share the steps when you do it. I'm very much behind repair. I rebuilt both mine and wife's e53 alternator


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jimoreno 02-10-2026 11:36 AM

The Valeo regulator is very easy to replace, no soldering required. However, finding the 230 Amp one proved impossible (or not economically feasible) when I was looking for one. When I was replacing the engine decided to take out the one in my alternator (@ 169K miles) and found out that the brushes were almost completely disappeared. There were some grooves in the slip rings also. I didn't realized it at the time that I had a 230 AMP regulator and purchased a 180 one just to be greeted with the "incorrect alternator" (or something like that) error message. Digging around I only found that Autozone had a 220 Amps CarQuest with lifetime warranty so I figured out that if it dies there are plenty of their store around. So far, so good no issues with it but only time will tell. At least in the N63 is right on top of everything (takes more time to remove the fan and serpentine belt than the alternator itself!)

josiahg52 02-10-2026 05:40 PM

Quote:

Originally Posted by Bdc101 (Post 1247588)
I just checked and Valeo is the original manufacturer for the 220-amp alternator on my 35d (according to RealOEM).


Part number 12317603775 is the voltage regulator and is only about $60 for a Valeo version. Andrew, do you know if I need any special tools to remove the voltage regulator? The last time I did this was on a Toyota about 15 years ago and it was just attached to the end of the alternator. But FCP has a bunch of "decoupler" tools in their section for the alternator. Just want to check before I take the car apart.


Edit: Nevermind, it appears you can access it on the back of the alternator if you take it off.

Valeo 220A and the same part number for my 2011 35d.

The decoupler is a overrunning or clutched pulley that diesels should have on their alternators. INA, BMWDieselParts, and Litens all make the correct pulley. I plan to use a Litens when I rebuild mine. These type of pulleys require a tool, not exactly a tool, but a technique to remove the pulley. Basically a socket with wrench flats and a hole to pass the Torx bit through.

andrewwynn 02-11-2026 12:48 PM

Preventative replacement of alternator?
 
You should notice that the slip rings wear almost exclusively on one polarity. When i change the VR but not the slip rings i will change the polarity of the slip rings. Much easier than changing the slip rings.

https://xoutpost.com/bmw-sav-forums/...eo-alternaror-

My second valeo refurbish. I swapped the brushes and slip ring polarity.

I came up with an easier method to swap the polarity by cutting the conductive bars going to the brushes and soldering jumpers.

I think that method may apply to Bosch VR though i will see if i can find a photo

https://uploads.tapatalk-cdn.com/202...6e327cbb92.jpg


https://uploads.tapatalk-cdn.com/202...7e8c9427df.jpg

A couple photos to show how uneven the wear is on the slip rings.

If the VR simply swapped polarity every restart the alternator would last maybe 50% longer. (would make both the slip rings and the brushes wear evenly)

Clavurion 02-11-2026 01:05 PM

This still slightly puzzles me how the wear is so different depending on the polarity of exitation on those gliding surfaces. The same current flows thru both of them anyways.


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