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  #1  
Old 11-30-2025, 03:11 PM
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Preventative replacement of alternator?

I found a new aftermarket alternator (for $80) that i was thinking of preventative replacing on my e70 N52 X5 with 211k miles


Or just getting it to have as a spare in case mine ever fails


Mine seems to still chug along well but is this something that fails out of the blue?
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  #2  
Old 11-30-2025, 08:42 PM
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I don't think so, I plan to at 200k, but I'm going to use a Bosch remanufactured or a BMW one. Rather do it once and using one of those will increase that odd.
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Old 12-01-2025, 12:10 AM
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They will always wear out the slip rings and brushes.

Having a spare is not a bad idea.


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Old 12-01-2025, 07:18 AM
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Who makes that $80 aftermarket alternator?
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  #5  
Old 12-01-2025, 07:23 PM
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I wouldn't ever buy Bosch again. I did that on my E53 and it lasted around 17k miles before it failed.


I was actually just thinking of this for my E70 though. I'm big on preventative maintenance and I think mine is original at around 146k miles. What would you guys go with if you were going to replace it? I am actually going to do belts soon so I could do this at the same time.
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Old 12-01-2025, 07:36 PM
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The Bosch rebuilt should be good but the new Bosch that I once ordered was chinesium. That market changes pretty fast and it's hard to keep up with what is good any more!
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Old 12-01-2025, 09:01 PM
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I put a Bosch rebuilt alternator in when I did the motor swap a few years and around 20k ago. So far so good.

I have the original alternator that came out of the x5 during the swap and there is a shop in town that claims to be able to rebuild the Bosh water cooled units. BMW states otherwise. Obviously they can be rebuilt, so is this just BMW steering business to a Bosch company?

I’ve decided to swap my original 4.4 over to the air cooled alternator as part of the rebuild, but maybe I’ll have it rebuilt as a spare.
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Old 12-02-2025, 01:56 AM
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I have a lot of spare this and that. Some oem or aftermarket.
Its a great feeling to need a part especially on a Saturday and to know you have that needed part on the shelf at home. Less stresses if you ask me! No waiting for even express delivery.

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Old 12-02-2025, 07:13 AM
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I had a refrub bosch fail on the 2nd or 3rd drive. I traded it in for a new valeo at O'Reilly auto. Came with lifetime warranty. There are O'Reilly throughout the country and alternator is a mission critical part.

I've rebuilt the valeo at about 140.000 mi. and it lasted 40-50,000. I didn't autopsy to determine the fault but it likely was other than the brushes and rings which is what i replaced.

The Valeo repair kit was only $20 at the time i would prob be comfortable with swapping in this $80 model and rebuild the current one for $30 say and have that as a spare.

It's not difficult to rebuild the VR and replace the slip rings.

The second time i rebuild one i just replaced the brushes and flipped the polarity of the slip rings since 80% of the wear was on one ring. Rather than replaced the rings i just set it to wear down the other ring basically resetting the wear clock 100,000 miles with $12 of brushes and an hour of time.

I have a thread on xo showing how to do the polarity swap. IIRC, i cut the conduction bars and soldered wires criss/cross to swap the polarity.


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  #10  
Old 12-03-2025, 01:45 AM
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Quote:
Originally Posted by 80stech View Post
The Bosch rebuilt should be good but the new Bosch that I once ordered was chinesium. That market changes pretty fast and it's hard to keep up with what is good any more!

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.
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