Our dishwasher (A Siemens SD6P1S) didn't react when pushing the switch on button. Before doing anything to it, I made sure to check if the circuit breaker hadn't tripped and that there was power available on the power socket. This being the case and the machine appearing to be powerless, the first potential causes of failure which came to mind were maybe a bad contact in the power switch or maybe some internal protection which had tripped ( I knew from a previous repair that the machine has a float at the bottom to detect leaks.) or maybe some door contact malfunction.
When opening the machine I first tried bypassing the power switch but the machine still didn't react. I also assessed that the door contact didn't really function like a general 'shutoff' and it seemed to be working fine so this probably wouldn't be the problem. I also didn't see any water at the bottom of the machine, so no leaks. I tried the float switch but the machine didn't react. Having checked the most obvious potential causes I was starting to suspect that there might be a problem in the internal power supply of the machine...
There was one box at the bottom of the machine from which all the wire harnesses started. It seemed to contain the control panel for the dishwasher.
Demounting the box and opening it up was not so straight forward but I managed.
When I pulled out all the plugs of the wire harnesses and removed the printed circuit from the box I noticed that a small black 'rocky' part remained in the box.
When inspecting the print, I quickly noticed that one of the IC's was missing a chunk. It seemed like I was lucky and the trouble shooting was going to be rather quick.
When putting the missing piece back in place I could determine that the part in question is a TNY264GN. It is a switcher IC which protects the machine against, among others, under and over voltages and short circuits. When searching the web, it became clear that this part often gets damaged on various appliances across various brands. I even came across a dedicated website which explains in detail how to replace this component: https://www.maakmijnwitgoed.nl/content/7-stappenplan-zelf-lnk304-weerstand-vervangen
I ordered 2 new IC's (to have a spare) and while waiting for their delivery I cleaned the labyrinth of the dishwasher (see lower).
When desoldering the IC I unfortunately damaged/removed one of the soldering pads of the pcb. So when I soldered the new IC in place I soldered a small wire on the 3rd pin to connect it to the ground of the pcb.
Afterwards I installed the print back in the box and connected everything and let the machine complete a full program to properly test it. Once the machine completed the program I assembled it completely and put it back in its' place. Problem fixed :-)
While waiting for the delivery of the new IC I decided to clean the labyrinth of the dishwasher.
A quick check of the history of the machine showed that the first time I had to clean this labyrinth was after 44 months of use. The second time I cleaned the labyrinth was 35 months after the first time. Now we were 41 months after the second time I cleaned it.... Chances were quite big it would give a problem again in one of the coming months. I decided to clean it pre-emptively.
The issue with the labyrinth, to my understanding, is that a valve, inside the labyrinth, which allows for the pressure inside the dishwasher to equalise to the outside pressure gets clogged up. The dishwasher somehow detects that the pressure is no longer allowed to equalise and gives an error.
The labyrinth is completely closed up and it has only a few little holes through which you can pour water and one bigger hole through which you can try to insert some brush. But due to its irregular shape it is very very difficult to get into all crevices and nooks.
The dirt which builds up over 3 years of usage is also very sticky...
Due to my previous experiences I have been able to develop a technique that allows me to clean the labyrinth for about 98%.
First of all I pour soap into the labyrinth and fill it up with hot water and I plunge it into the sink filled with hot water. The water I use is somewhere between 60 and 90°C so I wear rubber gloves to give my hands some kind of protection.
Once the whole labyrinth is warmed up I start to rinse its inside with soapy water while shaking and agitating it in all directions. When doing this, a lot of the dirt will come loose and will leave the labyrinth through the big opening.
This will allow to remove the bulk of the dirt but in the crevices around the valve dirt will remain and will require some mechanical assistance. For this purpose I use a steel wire which I bend at the end (about 3-4cm).
The steel wire I use is about 2mm thick.
The position of the steel wire bent in 90° indicated with yellow dots.
I insert the wire through the big hole into the narrow channel upwards. Once the channel widens the springy wire jumps open and latches behind the plastic. When I now pull on the wire I am able to bend it into an almost 90° angle. I can now move it around a little in the nook and together with some soapy hot water it dislocates any large chunks of dirt which remain.
Once more or less clean it suffices to pull the wire hard. It will more or less straighten out and I am able to pull it out of the labyrinth.
Once clean, the labyrinth can be installed again. Connect the flow meter and both hoses on the outside. Make sure not to forget the rubber seals for both openings to the inside of the dishwasher. The small cap/drain on the bottom can be tightened using a socket wrench and the big cap/drain can be tightened with an Allen key.
Some tips how to keep your dishwasher clean and avoid/postpone clogging up of the labyrinth:
Rinse plates, pots etc before putting them in the dishwasher. Make sure no solid food particles enter the dishwasher. Pay special attention to seeds from lemons, apples, grapes, etc. They take really long to decompose and can jam up your dishwasher.
Clean the filter at the bottom regularly. Any dirt remaining in it will cause smells...
Clean the rubber seals of the dishwasher door with some soapy cloth when they are dirty.
We always use the 'eco' setting which washes at 50°C but once a week, when the machine is extremely fully packed, we will use the 70°C program. I hope that the hotter water helps to wash remaining grease away.
Once every 4 months we will buy a special 'bottle' to clean the machine and give it an empty washing cycle.