My 1989 310,000 mile Volvo 240 wagon's Brake Failure Light comes on sometimes, and stays off other times. Typically, it either comes on when I start the car or it doesn't, and it will stay on or off for the entire ride. Brakes seem fine, but I am very cautious and brake very early when it is on.
Any suggestions?

When this happens in my cars, I have the unpleasant job to clean the rusty, waterlogged brake fluid out of the switch port of the Brake Failure Warning Sensor. The O-ring seals on the pressure side of the shuttle eventually pass a bit of hydraulic fluid into the switch chamber. The unpleasant part of the job is working under it, and removing the ring of rust that makes it difficult to start the threads of the nylon switch body back into the casting after all is washed out. But not as bad as replacing the octopus. I like it better when the car exhibiting your symptom is 91 or later, because that just means it needs brakes; the fluid level is sloshing the float around.














--
Art Benstein near Baltimore

When a clock is hungry, it goes back four seconds.

Fred, it it dangerous as it is?
Do I need to do something about it?

"Fred, it it dangerous as it is?
Do I need to do something about it? "

In my case, it wasn't at all dangerous. A false alarm. But your case is only likely to be like my case, not certainly. So you need to have it investigated.
--
Art Benstein near Baltimore

She had a boyfriend with a wooden leg, but she broke it off.