One problem related to brake light on has been reported for the 1999 Ford Ranger. The most recently reported issues are listed below.
Truck lost brakes while going downhill. Frame corrosion had caused right spring hanger to fail, and corroded brake line burst. I was able to pump the brake pedal and avoid an accident. Brake warning light came on after the incident. Mechanic put the truck on a lift, and identified severe corrosion to the brake lines, differential, frame, and several other undercarriage components. Truck had been undercoated and washed regularly, and has less than 105,000 miles. Mechanic suggested all new brake lines, total frame, and rear end replacement.