Switch assembly, including a fixed contact part, an elastic switching contact part, a mounting plate, wherein the fixed contact part and the switching contact part are located on the mounting plate, the switching contact part having at least one extension that projects beyond an outside surface of the mounting plate upon installation and in an operating position such that when the switching contact part is exposed to pressure in a direction of the mounting plate, an electrical signal between the elastic switching contact part and the fixed contact part will be either interrupted or established. A fixing mechanism pretensions the switching contact part prior to installation such that the at least one extension does not project beyond the outside surface of the mounting plate. The fixing mechanism releases the switching contact part tension when the switch assembly is installed and in the operating position.