How old is the battery? If you are sure the battery is good you can use a multimeter and start pulling fuses one by one until you isolate the cause of the drain. As a side note I once had an old BMW that would constantly drain the battery after about 3-4 days of sitting. Turned out the trunk light was staying on.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record