In the UK it’s very hard to get circuit diagrams or repair manuals. I get many emails from people looking for repair manuals and wiring diagrams for white goods appliances, but they are only available to the trade. Even then they are commonly only available by opening a trade account, paying a subscription and logging online into a manufacturer’s secure technical support web site. Another common way the trade can have access to them is by subscribing to them on DVD, which isn’t cheap, and needs renewing every several months or so. Gone are the days when we used to buy the wiring diagrams and repair manuals in printed form.
Remove the adjustment mechanism it's often part of the bracket holding the switch in place! As for identifying the pressure switch, that's easy. Nine times out of 10, it's directly behind the 'water level' adjustment knob in the top control panel of the machine. If the machine's upside down or partly destroyed, follow the sensing tube from the base of the wash tub. And while you're at it, it's also usually worth scrounging the tube, which is often a high-quality plastic hose. You never know when it might come in handy.By contrast, dishwasher pressure switches are normally buried beneath the stainless steel drum.