I don't know what fuse, but the alarm system can also be a problem / phantom drain, and your radio going into lock mode is an interesting clue. If you need to unplug the alarm system, roll down the carpet in the passenger footwell, remove the screw and plastic panel from beneath, and unplug the small box marked BECKER. Don't unplug anything red, that would be airbag (but I don't think there's anything there, the controller is under the radio).

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Gone to the dark side

- Jeff