do you mean the "low brake fluid warning light" or the lights at the back of your car? "low brake fluid warning light": can also be caused by worn out brake pads, or some cable which is connected to the lever in the brake fluid tank is lose or lost its connection to the lever and/ or its mechanism. --> check the cables and their connectors which route to the lever in the brake fluid tank, check the brake pads front and rear. lights at the back of your car: switch at the brake pedal gone bad, or water and/ or corrosion in the back lights which causes contact between negative and the positive pole of the brake lights. --> check the switch at the pedal (maybe a new one isn´t that expensive), check the rear lights for water and corrosion