Dishwasher Help Forum

[snanceki]

Hi Guys...I need you expertise PLEASE!!
Well I decided to have a go at getting the above m/c back up and running. It has been in my garage for several years after exhibiting a fault but I can no longer remember exactly what was wrong.
Now I have double checked EVERYTHING on this m/c and have therefore concluded that it must be the ECU. However I hold the view that ECU's rarely go wrong )at least after normal "burn in". (Bathtub reliability curve). The ECU looks fine (no dry joints) and the relay contacts are working OK when bench tested with 12v
The water IN solenoid measures 2.2k ohm (1/10a), the boiler element measures 238 ohm (10a), both pumps and the assorted switches all test OK electrically. There is no water in the base of the m/c and the flood micro works the exit pump when lifted.
I reset the ECO Buttons 1 & 3 > 3 secs) and the appropriate cycle and "End" light/ buzzer operated. I selected a different programme and closed the door. The exit pump started and stopped after a few seconds but nothing further.
Now something strange in the wiring caught my attention as I was reverse engineering the circuit diagram. The feed to the boiler is thru a micro switch on the end of the element. I took this to be a reset (in case of over temp or similar) but couldn't understand why the attached micro switch which is wired in series is normally open (NO) hence preventing any power getting to the element. On thinking about this I guess this switch MUST BE a water pressure present switch. Maybe somebody could confirm this if correct - in which case this issue is resolved but it does nothing to resolve what is wrong.
I carry out auto electrical (digital) repair and hold the view that ECU's give little trouble. It's usually the connections that are at fault or water ingress into the PCB.
Help guys. Any tid bits that you can offer would be much appreciated. Spending mega bucks to replace the ECU (and it may not be at fault) just doesn't make sense even though the m/c looks nearly new.
Is there such a thing as an ECU sequence (programme) chart available"?
Regards. Stuart.

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[Martin]

Wow that's a lot of text to describe one symptom Stuart. But, correct me if I'm wrong but I think all you're saying is that it simply doesn't fill....right!

[snanceki]

Hi Martin,

Thanks for getting back.
OK It doesn't fill!
So I'm left waiting for your valuable input

Having read a blog on an equivalent German site to yours it appears that the AquaStop solenoid causes the controlling Triac on the ECU to fail if the m/c is ON with no water available.
Interestingly it appears that many people are trying to track down Z9MY triacs without success. FYI The full number for these happens to be ST Microelectronics Z0109MN. (1a / 10ma sensitivity). I'm off to Maplin today.

I'm waiting for your input.

[Martin]

I'm waiting for your input.

When triacs fail, almost always they blow up and the top section is missing. Easy to spot in fact!