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Malfunctioning brake warning light/sound - Buick Riviera

I own a 1997 Riviera that has recently started lighting up the Brake Warning light and associated chime sound under moderate acceleration when the car and the air are cold (below 50 degrees f. outside). Easing up on the throttle will stop the warning. The brakes work just fine. As the car and air warm up, acceleration does not cause the warning.

Is this a known issue? It seems very odd that a brake warning would occur on acceleration. I?m guessing that an inertia sensor may be malfunctioning. I?m not comfortable taking it to a dealer without some idea of what might be required to fix it. Can you provide any information?

Two things will turn the light on. Either the parking brake is not completely off thus activating the switch, or the fluid in the master brake cylinder is low enough to trigger the light. As the brake pads wear, it takes more fluid from the master cylinder to take up the extra space in the wheel cyinders. That can cause the fluid to get low enough in the resevoir to trigger the light. Movement of the car can make the fluid slosh around some to turn it on and off in corners etc. Also, the switch in the master cylinder can just go bad triggering the light when nothing is wrong. The switch can’t be replaced alone though and requires either a new tank or new master cyinder. If the brake fluid is at the proper level, you can simply unplug the wire going to the master cyl. and if the light goes out, that’s where the problem is. I’ve never heard of an inertia sensor in a Riviera so not sure what you are talking about, but that’s not it.

I will check the fluid. The light doesn’t come on when the car is stopped, so unplugging the wire won’t help diagnose.

I agree with Bing. I suggest you check the level of fluid in the brake reservoir. Low fluid is the most likely reason for the warning light to come on under the conditions you describe.

I’m unaware of an inertia switch associated with the brake system.

Why do you want to take a 12 year old car to the dealer?

Unplugging the light and driving the car might help diagnose. If you accelerate hard with the wire disconnected, and the light doesn’t come on, but it does come on under hard acceleration with the wire connected, it should tell you something.

Check the fluid.

When was the last time you replaced the brake fluid. If over three years, it likely is past time to do it. Start there and have them check to see if it is low or if there are any leaks. They should do this anyway, but ask so they will let you know it was or was not OK.