The Preamble:
In ancient times, the psy were considered Napoleons, but tempora mutantur is known. Now they are all electricians and household appliances installers.

So, a fable from one professionally-oriented forum from a current and respected professional of his case:

The real story - fifteen years ago, the fairly steep citizens had a fairly steep Siemens washing machine. And something she did not work, according to customers - can wash almost a whole day and all "took in one place." The replacement of the timer, the module, the TEN, the pump, the engine did not make sense, well then Bosch-Siemens was very loyal to such things. Moreover, with the master everything works, a few washes the master from Bosch-Siemens almost spent with a second meter next to the washing machine - everything works like a textbook. Voltage - exactly 220 V through a specially purchased stabilizer! I went to the hospital several times - it all works! But the customers don’t want it and it’s all there!!! For the tenth time the master looked closer at the wiring and fell into a precipitation - the washing machine was connected through the switch in the bathroom and worked only when the light was turned on! Naturally, when the master came, the light in the bathroom was turned on and the washing went from and before, as needed. And without the master, the housewife will load the washing machine, turn it on, wait a little while until it starts working, then leave the bathroom, turn off the light, the washing machine and "sleep." The mistress after some time will decide to check how the laundry is going, will turn on the light in the bathroom, the washing machine will turn on, the aunt in the door will look - as if everything works... She will turn off the light again...