Typically, washing machine pressure switches have a large sensing diaphragm that's about 60mm or so in diameter and three quick-connect male terminals. One connection is common, while the others are for normally open (NO) and normally closed (NC) connections. A set-point adjustment mechanism is built in (it's directly controlled by the 'water level' knob) and the switch opens and closes with audible clicks.
Most appliance manufacturers have now found it advantageous to employ a small switch or micro-switch, to stop the spin action. An actuator protruding from the lid of the automatic washer causes the switch to open before the lid is raised 2 inches. Electrical, either type of spin-stop lid or door safety switch is usually connected to wires between the spin solenoid and the timer. In this way, when the operator raises the lid during spin, the switch opens and the timer circuit to the spin solenoid is broken. By keeping the actuator clean and free of debris, you can avoid unwanted appliance repair service calls.