Abstract: A pressure switch including a housing 10, electrical contacts 16, 24 within the housing and a lever 26 movably mounted within the housing and operable to effect relative movement between the contacts. A biasing spring 70 biases the lever in a first direction and is settable through elements 74, 76, 78, 80 to determine the pressure level at which the switch will operate. An over center device 36, 38, 40, 42, 44, 46, 50, 52, 54, 56, 58 is located within the housing and is connected to the lever to provide snap action movement of the contact. A pressure port 96 is located in the housing and a fluid motor including a rolling diaphragm 116 is in fluid communication with the pressure port and acts in opposition to the biasing spring 70.