It's easy to find,
1 Disconnect your negative lead on your battery
2 Put a cheap test light between the cable and the battery
3 If the light is on you have a leak so start removing fuses until the light
goes out, that is the circuit the leak is on
4.You could just leave the filter out during extended stays if you can't
identify the actual leak.
5. I'll bet it's the fuse which controls your dash clock, radio and interior cab
lights.
(I think its the 4th fuse from the right)

I've had the same problem but if I remove that fuse the battery stays fully
charged.
Paul Borghese wrote:

Tony 85GL "Westfailure"

>

> Hi,
>
> My 1985 Vanagon has a slow battery drain where if left for a few weeks the
> battery will fully discharge.  Any idea on how to troubleshoot and find such
> a problem?
>
> Thanks,
>
> Paul Borghese