Alternator Issues Again

[DougPEX5]

I have been experiencing either a bad run of alternators, or my X5 is just mad at me not buying BMW parts. I have the 4.4 motor with the 150amp water cooled alternator. I am now going on my third alternator from NAPA. First one was a cheap $440 one that lasted two years. So since that failed I thought I’ll turn this in for the free lifetime warranty and also upgrade to the remanufactured Bosch for an additional $330. Worked fine for only 13 months now this one is drawing 4 amps with the vehicle off. I assume the voltage regulator has shorted.

Has anyone had good/bad long term results with any alternators???


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[Bdc101]

I used a Bosch reman unit in my 3.0i that I had to replace exactly three years after I put it in (I just replaced it in Feb). I have heard other horror stories about those units as well. I put in a Valeo reman unit this time. Buy from FCP for the warranty to be safe, if you're worried about it.

[Effduration]

Bosch sold its reman rotating unit (starters and alternators) to a group of Chinese investors a few years ago. I no longer buy them.

New Bosch is fine. I also get my Alternators rebuilt form a local rebuild shop with a long history and a good reputation.

[80stech]

Alternator quality is a crap shoot. Any parts store like Napa etc. is going to be dicey. Rebuilt Bosch 7 or 8 years ago was good, still reman'ed in Germany and was more expensive than the new Bosch which was made in China at that time. The best thing to do is go to a local rebuild shop like Effduration says, if you have one near-by, or try to get one that you can get some confirmation on the quality/reputation. It's not uncommon to have multiple bad crappy alternators.

[X5chemist]

Ouch. I would start looking all body grounds. Add a few too. You can't never overdo grounds on a vehicle. I recently did some on a Benz C240. I was surprised the entire battery ground has only two points. Multiple body and engine grounds were added.

[oldskewel]

4 Amps is about the right number to be flowing through the field windings (through the slip rings) at battery voltage. E.g., 12V supply, 3 Ohm field winding resistance = 4 Amps current through there if the negative side of the windings is grounded.

So that might give you a clue about where to look for the problem in case you are thinking about diagnosing or even fixing it yourself. I know it would be nice to just get a free replacement one that works, but ...

Sometimes, as I've noticed on a reman alternator purchase many years ago on a different car, something as simple as using little Phillips head screws that hold the VR in place, etc., which are too long can cause an internal short. I.e., the screw is supposed to hold the VR to something, but since the screw is too long, it goes through further and barely, intermittently, maybe after a year of vibration, touches a ground, leading to a problem like this.

Could also be a failure within the VR circuitry that holds a switch open when it should close. That would be exactly the sort of thing Chinese companies are notorious for - cutting costs on electrical circuits, since they can work perfectly for a brief period before failing once they are off the hook.

[CLS70]

I’m dealing with similar issue….
The original alternator failed, replaced with a new one (not OEM) which failed within hours; got a replacement (same model) which lasted 5 days…..
I had put two new ground straps so I hope that is not the issue
No idea what else could be behind - any suggestions?
Note it is an e70

[X5chemist]

Try registering the battery with a new alternator. Today's alternators have variable charging. If the DME is using old data to charge an old battery, it could destroy itself. It drives me nuts not seeing constant voltage on these new vehicles. Especially since they are so picky with voltage.

[CLS70]

Ok - will give it a try....but is that an option? e.g. registering a new alternator? (vs Battery)

Now, if I disconnect the IBS, should the Alternator go into default charge values? (want to test that the alternator is still working, as if that is the case do not need to disassembly/replace -- again.)

[EODguy]

Registration of the battery didn't start till the e70 series X5 so you are fine there.

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