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