Well, two more things to scratch off the list. I disconnected the connector going to the radiator fan switch - still getting 4.2 amps of current flow. Same thing when I disconnected the connector going to the (aftermarket) ipod connector.

As far as checking whether the alternator is the culprit, what's the best way to do that? Will disconnecting the connector going to it be sufficient?

Any other common causes of a leak this size that I should check, before I go through the tedious exercise of removing each fuse one at a time? Thanks.

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