BRAKE light on 2001 S40

[et]

BRAKE light comes on sometimes, stays on for length of a drive.
Turning off, waiting 20 seconds and restarting doesn't make it go away,
but a few hours later I start it and it's out.

What does this mean?

 

[Marvin]

BRAKE light comes on sometimes, stays on for length of a drive.
Turning off, waiting 20 seconds and restarting doesn't make it go away,
but a few hours later I start it and it's out.

What does this mean?

Probably a faulty switch that responds to braking fluid
pressure. I had that on a Saab, and didn't notice it until
the light burned long enough to run my battery down.