Takes some water, makes a few spins and after about 10 sec gives error F23.
I checked all related topics in this forum, and tried almost everything.
The hose to the pressure switch is good, it actually switches when the machine takes water. In any case, I replaced the pressure switch with a new one. The cables connecting the pressure switch to the main board are good.
I checked the heater, it also looks OK. There is no leakage. I disconnected the heater and switched a lamp on its place -- same error, although the lamp doesn't lit (that's probably because the error appears before the heater switches on). I also checked all three relays on the main board -- they also appear to be working.
When I disassembled the board, I noticed a dead centipede on it. Is it possible the bug to have caused some damage to the board? There are no obviously burnt elements. As advised on a Bulgarian forum I checked the 470K resistors immediately after the pressure switch and they were all OK.