Brake warning light on the dash Mercury Grand Marquis 2002 model

If the brake fluid is full the float that is in the reservoir may be stuck down and causing the light to be on. The e-brake also has a switch near where the pedal is when released, it can go bad or not be pushed in if the pedal isn't all the way up. While pulling the brake release lever use your foot to lift up on the e-brake pedal. While looking in the master cylinder use something like a clean pocket screwdriver to tap on the float to make sure that its up all the way.