Exceptions. I’m talking about the UK. It seems that there are plenty of schematic’s and wiring diagrams available for American appliances on USA or Canadian repair sites, but not so much for the UK. Some washing machines and other appliances have been known to have a wiring schematic under the lid. I know Miele and a few other quality appliance manufacturers used to place a basic wiring schematic on top of the soap dispenser or underneath the lid. This does not happen on most washing machines though, especially the cheaper ones and they are often very basic
At times you may feel your laundry is not coming out as clean as it used to be, then also you can doubt the possibility of an error in the heating element. Most probably the clothes might not be getting hot water and consequently they might be getting washed in cold water!