My 83 V doesnt have the float switch on top of the brake fluid reservoir -
hence brake light on is a result of a pressure difference between the
front and rear fluid circuits, ergo leak or bad mastercylinder, or ....

its possible you have a parking brake switch that is flashing, maybe when
you brake hard ???  The 'brake' light on  the dash can actually be turned  on
two ways - fluid pressure differential and by the parking brake being out
of the fully released position. Once had a friend with a rabbit who chased
brake light for 6 months before realised the parking brake switch was
popping out of position when she drove - it took about 15 minutes so it was
a real toughie to diagnose until you looked at the problem the right way.

Bottom line is - are your brakes up to snuff?? Find another vanagon owner
and ask to drive so you know how they compare (just drive to the nearest mall
and ask the first V owner you see - they're cool invariably ...

:-)