Thanks for the replies - makes me feel like I'm not alone in this.

No luck so far - I pulled all the fuses people had posted as potentially protecting the blower fan circuit (64, 34, 48, and 9), and I get the same 4 amp draw each time. So, this rules out the FSR. I also pulled fuse 74 (Telephone Control Unit, apparently another common culprit), and same result. And just because they're easy to get to, I pulled each of the fuses in the rear fuse box, one at a time, and got a consistent 4 amp draw each time.

I did all this before opening this thread, so I'll next check the aux radiator fan, but it's getting late, and I haven't had dinner, so this will wait till tomorrow.

If that turns out not to be the cause, I'll take it to an auto parts store to run an alternator test. I'll report back what I find, and in the meantime welcome any other ideas. Thanks.

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2003 X5 4.4i
1992 Porsche 968
2007 328i
2014 Subaru Forester XT