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.
The motor cannot be reversed instantly. It needs a brief pause between switching directions, or else it may get damaged. For this purpose, another spin direction control timer (IC2) is employed. It is realised with an IC 555. This timer gives an alternate ‘on’ and ‘off’ time duration of 10 seconds and 3 seconds, respectively. So after every l0 seconds of running (either in clockwise or anticlock-wise direction), the motor stops for a brief duration of 3 seconds. The values of R3 and R4 are calculated accordingly.