On Sun, 28 Jun 2015 13:40:49 -0400, "Mayayana"
wrote:

| There is a float switch in the reservoir, and they can be "flakey",
| triggering the brake warning light even with the fluid at the correct
| level.

That could explain the light going
out when he tops it up. Maybe the float
switch is sticking. Now the question is
where the heck is all of his brake fluid
going to?

Well, for starters, check the front brake pads. When the pads get worn
down to the "limit" the fluid level should be about low enough to turn
on the light. Replacing the pads and pushing the pistons back should
restore the fluid level. Good idea to drain and flush the fluid at
this time as fluid is hygroscopic (absorbs moisture) and moisture will
settle to the lower parts of the system, corroding the calipers and
pistons.

He could also have a leak in the master cyl, steel lines, flex lines,
calipers, or rear cyls.