Is the brake pedal suddenly mushy, car doesn't stop good?
First check your brake fluid one reservoir may be empty, or near so.
It sounds like your balance valve may have moved off center, causing the brake light all the time.
If the fluid went away, find out where the leak is, hose, tubing or wheel cylinder. Ten fix the leak, fill it up. You'll have to bleed the brakes in a certain sequence to get the valve back to center...
I had this problem with a similar model car. It turned out I had a brake cylinder leaking on a rear wheel. It's a pretty simple repair (if you can get the drum apart). It could be other things, though, too including an electrical problem. I'd just have a break inspection done. Some shops will do that free, but I've paid as much as $30 for one.
That could b brake fluid.r could b ur shoes r pads r at their limit, Ders a senser in ur brakes ta let ya know when dey need ta b changed!! just ta pass ur test take the bulb out!!!! but do get ur brakes checked!!!!!!!! good luck!!!!!!!!!!
I think the Buick has the pedal style parking brake. It is probably the return spring in the pedal assembly. to check raise the pedal by hand and see if the light goes off. If so, secure it in that location. I believe to fix you have to replace the p-brake assembly.