Automotive auxiliary systems which derive power from the engine are becoming increasingly important in terms of fuel economy and safety. These systems are thus becoming major targets for reliability and efficiency improvements. The emergence of a new generation of control components is contributing greatly to the success of this effort.This paper will address how new pressure switch designs and applications are helping to improve the function, safety, and efficiency of auxiliary systems such as air conditioning, power steering, power brakes, and electric engine cooling fans.All of these systems have a common factor. They either generate fluid pressure directly or respond to changes in fluid pressure. A new family of snap-action disc type pressure switches is uniquely suited to control the operation of these systems.