2005 X5 M54 Alternator replacement questions

Bottomfeeder · #1 08-19-2021, 05:53 PM

Hi All -

A bit of background first: A few weeks ago I pulled into a shop and when I came back and started the car (2005 BMW X5 3.0 with 33500 miles) the battery light came on, accompanied by a bit of a whining noise. The noise was not loud by any means, but the car's quiet enough that I definitely noticed it.

I was only a mile or so from my home and had one more stop to make. Got out, got back in, restarted the car and -poof- no battery light or whine. When I got back home and researched, it seemed pretty obvious that an alternator replacement might be looming not too far on the horizon.

But the light never came back on, and I drove it as usual. Until today ... the light is back on, the whine is back, and whatever forces of good luck that made the problem go away the first time seem to have left the building. Sigh.

So today I put the battery on a trickle charger for a bit and it charged up just fine. Shows 12.4 volts resting. When the car's running, however, it drops to around 11.6. Seems like pretty classic alternator failure, but is there anything else particular to these models that I should be looking at?

So here's my next question - looking at the online vendors, it looks like there were several different alternators available. Is there any way to tell by the VIN number which one I need? Hoping I can order it before having to remove the one I have.

Second, I'm wondering if anyone has any tips for the job. Looks pretty straightforward, though clearly some stuff has to come out to give my fat hands access.

Thanks in advance for any tips, tricks, or general wisdom. I've had two of these old girls in the garage (a silver 2002 and this black 2005, both M54s) for a couple of years now and am still learning my way around them. So far so good!

Best regards and thanks in advance,
Chris

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andrewwynn · #2 08-19-2021, 07:48 PM

Find out of its valeo or Bosch alternator. If Valeo there is a $20 refurbish kit to replace the slip rings and brushes. I did that on both our m54.

It may be just the VR and those are not expensive for the Bosch but are like 40% of the price of a new valeo.

Bottomfeeder · #3 08-19-2021, 09:05 PM

That's one of the main things I was wondering ... if there's an easy way to tell which alternator you have, either by VIN or visually. I don't rely on this car for everyday transportation and I can pull the alternator to confirm what I have before ordering if I need to, but I'd love to have the right part in hand before I start doing the work if I can. Call me lazy. :-)

andrewwynn · #4 08-19-2021, 09:09 PM

Reasonably big inspection camera you should be able to see the name on the back of the alternator.

And won’t tell you which brand but it might tell you which amp

Bottomfeeder · #5 08-20-2021, 05:43 PM

Not having an inspection camera, I went out to the garage earlier today to start pulling the alternator. As luck would have it, the label is on the top and I was able to verify that it's a 140A Valeo. Part is on the way!

-Chris

cn90 · #6 08-20-2021, 06:22 PM

If you truly have only 33500 miles (as in the first post), then likely bad VR.
As mentioned above, you can find a Valeo VR kit on ebay for cheap.
If you are skilled, then you can even replace the VR with the alternator in situ.

Bottomfeeder · #7 08-20-2021, 07:40 PM

Mileage is indeed 33500, and they've been easy miles. The car was maintained at its original dealership by the first owner until I bought it at just under 18000 miles on the clock. Always garaged. Hell, still smells like a new car.

I, too, wouldn't expect an alternator to go bad at this mileage, but considering the age of the car nothing would really surprise me. :-)

Two things make me think it might be the alternator itself rather than the voltage regulator. First, the whining noise that appeared as soon as the battery light came on. Second, I noticed a bit of a "burned electrical" smell under the hood when the problem resurfaced. But on second thought that could be the VR, too.

Maybe I'll try the VR replacement first. I think I had assumed that the voltage regulator was integral to the alternator. Never good to assume. :-/

Thanks for the good counsel!

-Chris

andrewwynn · #8 08-21-2021, 04:56 AM

If VR breaks it can offer an uneven load (example of one of the three windings opens) which will make a very distinct him that will sound like a bad bearing.

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cn90 · #9 08-21-2021, 10:52 AM

If you break down the components of a typical alternator...

- Bearings x2: these last some 200K-250K.

- Windings > 200K. Rarely ever goes out.

- Inside the so-called VR is actually 2 parts:

* Brushes: look in bimmerfest E39, but after 180K, they are worn down.
At 200K, they are basically gone. The copper rings are also worn at 200K.

* The actual VR itself: being an electronic component, this lasts anywhere between 30K-500K. Completely unpredictable. This is exactly where the problem is...

Bottomfeeder · #10 08-21-2021, 04:34 PM

Thanks to all for the advice! I would have to agree that the VR does seem very likely to be the culprit of my problems. If I hadn't already ordered a new alternator I would probably start there and give it a try. But having a brand new part with a lifetime warranty in the car isn't a bad thing either. :-) Think I'll keep the existing one, put a new voltage regulator on it, and keep it around as a spare.

Thanks and regards,
Chris

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