I own a '98 Sable. When you look under the dash at the brake pedal, you will see the typical Ford brake light switch that connects to the brake pedal arm that activates the brake lights. What is the white plastic 'plunger style' arm behind it? It moves with the pressing of the brake pedal too. It appears to be an electric switch of some kind. The wires from it connect to the brake light switch. What is it and what is its purpose??