Grab a multimeter and test across each fuse to see which one is drawing current while the car is off. That will narrow down the possibilities. The dash draws a little current for the clock but it is overall negligible (same with radio and memory seats).

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth