You need to check all the circuits for a drain. That's done by removing
each fuse, one by one, and checking its circuit with an ohm meter or
test lamp. The one with a short or drain will light the test lamp or
show resistance on the ohm meter. Only the clock is a legitimate draw.

Power antenna motors sometimes get stuck ON. You can disconnect its
motor at the antenna - and still have radio if the antenna is left in an
UP position.

Another possibility is a window motor that's ON due to a stuck switch.

Wipers seem to get a shot of power whenever the starter is used -
somehow getting power from the start circuit or ignition switch. Anyone
ever "work" on the car's wiring - to install a stereo or alarm? If so
I'd first look there.

Rooster schrieb:

Perhaps a bad or no motor-ground connection.

Alternator may be not working.

Check belt tension, battery voltage difference with and without engine
running, alternator loading lamp in the instrument cluster and the
graphite contact in the alternator as well as the voltage regulator unit.