New behavior recently in my '84 Wolfsburg Westy.

The brake warning light comes on bright when the hand brake is set.

When I release the hand brake, the warning light goes dark.

While driving, the brake warning light comes on, not as bright as usual.
  At that point, if I set the hand brake, the light goes bright, then
back to not as bright when I release the hand brake.

When I step on the brake pedal, the warning light goes dark.  The brake
pedal feels normal, so I don't think one of the hydraulic circuits is
out.  When I release the brake pedal, the warning light goes back to not
as bright.

If I read the Owner's Manual correctly, the warning light is supposed to
come on when I PRESS the brake pedal and one of the hydraulic circuits
is out.  It's not supposed to be on when the brake pedal is NOT engaged,
even if one hydraulic circuit is out.  Is that right?

So is this just an electrical short?

In some cars, the brake warning light comes on when a brake light bulb
is out.  I don't see any mention of that in the Owner's Manual.