Washing Machine Diagram / August 25, 2018 / Amber Dumas.
Washing machine pressure switches directly control the hot and cold water inlet solenoids and so are rated for quite high currents - 15A at 230V AC is typical. So for low-voltage DC applications, the switches can certainly cope with (say) 5A. This means that, for most loads, a relay won't be needed.
If your washing machine does not heat the water during its wash cycle, it is likely to need some kind repair, a faulty water heater element is the most likely cause for this type of problem, here are a few checks that you can use that will indicate to you whether you have a likely faulty water heater element.
Basically, a single-phase motor requires a master timer, which decides the time for which the motor should keep rotating (washing time), and a spin direction controller, which stops the motor for 3 seconds after every 10 seconds and then resumes rotation in opposite direction.
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.