:confused: 1991 Buick Century with 2.5 L engine. For 2 months Brake light stays on when running. Brake fluid is not low. Brakes work great and have been checked out.

Now the battery light comes on when engine off. 4 hours battery dead.

Can jump start car and runs great. The battery and alternator is good on Advance Auto Parts tester. (while both in vehicle)
What is the problem or problems?

I've worked with the testers at Advance and Autozone for 8 years. They are not always 100% correct. For peace of mind, I would take off the alternator and have it bench tested.

Welcome to the forum!

You're referring to the Brake warning light on the instrument cluster rather than the rear brake lights, right?

-Rod