At 05:36 PM 9/1/2008, Cullen Stewart wrote...
>I have a 2 new interstate group 41 batteries and the stereo is hooked
>up exclusively to the aux. battery. That battery goes completely dead
>overnight without any other usage beyond the clock on the stereo.

The ONLY way to know for sure is to put an ammeter in line with the aux
battery. See what it draws with everything off. Then disconnect the
power to the stereo and see what difference that makes.

All modern head units have two power leads - one goes to constant +12V,
and provides power to the unit, the other should go to a switched
(ignition on) +12V. Since the Vanagon doesn't have an aux position on
the keyswitch, connecting it to the door buzzer circuit can provide
that function, and allow you to play the radio as long as the key is in
the ignition.

If you connected BOTH power leads to +12V, then that's a problem.