Take the Ground (Negative) strap off. Look for any little sparks
as you do; that'll be a tipoff.
Then, connect a small 12V pilot lamp (speedo bulb maybe) in series
with the Negative cable (one side of bulb to chassis, other side
to the battery Neg post. Does it light?
You can also use a multimeter in place of the bulb. Set it on
the highest Amp/milliamp scale to start.
If you get a bright light or more than 50 milliamps, pull fuses
till it goes away.
If you get a high reading and pulling fuses doesn't stop it,
the alternator could be at fault; try disconnecting it.
Lots of ways to skin the cat, but that's one route to start at.
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