Have copied your post here to clarify your issue...
I have asked a couple of questions below ..... also, have a few suggestions to try (if you can be bothered with it!)
1.you checked your pump motor and actually fed the required voltage (see what voltage the pump motor is, I would suspect 230/243VAC) into it to confirm it is spinning and not causing a short? If it is shorting then there could be a back voltage feed that is loading up the main board (just a hypothesis – not sure).... I say this because in your post you mentioned that the water was stil in the bottom .... which indicates to me that something went wrong when it went to pump out during the cycle.
2. Are there any machine fuses that may have blown? Or VDR’s perhaps? There is a VDR on the board that will blow and protect he main control board with it overloads (kind of an electronic protection ofr a circuit.) – take a look at my posting and you will see my photo and I have replaced that VDR I am sure it was a 285Volt AC VDR..... any electronics service shop will have them!
3. Heating element ok? Have you tested the heating element to make sure it is not stuffed? Also check the connections and wiring to and from the heating element to make sure you do not have any high restance connections in the circuit.
I recently repaired a pie warmer machine that nearly caught fie due to high resistance connections (and a faulty capilary thermostat). All the wires were hardended and brittle due to excessive ressitance causing heat!!!!! Lots of it.
Perhaps we can assist one another to test the boards .....re can compare circuit ohms readings on each resistor and capacitor etc!!!!! Since mine actually works most of the time.... it could be a good working platform to work from.
PS. Apologies for the war and peace novel .... but just trying to help and logic is my best gift when coming to diagnostics.
YOUR POST SAID:
Thanks for trying to help out....
The d/w was put on a long wash cycle one night and, next morning it was still "working"...!
When opening the door you could still see the water (not sudsy) churning around....no control panel buttons were lit ..and I'd expected the machine to stop but it didn't.
Had to turn off at the power point. Turned on again later..same problem.
A technician was called and seemed to think it was a control board (circuit board) problem but could not discount other things. The cost of the circuit board was prohibitive ( More than half the cost of a then new machine..) so I decided to have a go myself with some initial guidance from the technician.
1) Removed and checked the water control valve solenoid..clean and worked fine under power (passed water okay)
2) Checked every hose, chamber, supply hose, spray arms etc..No blockages. Motor could be turned freely via a screwdriver slot at rear of main shaft which was protruding at base of machine.
3) Checked main door switch...It had 80 ohms resistance so swapped it with another s/h spare (zero resistance when activated). Good , that would have been an issue
4) Checked air operated pressure switch...2 main switches operated in 2 stages when blowing air through connecting tube...1st stage zero resistance..second stage "click" cut off the circuit/s.
5) Removed/cleaned/checked the membrane strip..all clean and tracks look intact. (Did not know further how to test it..?)
6) Checked continuity of temperature overload switch..okay on room temperature setting (did not test it with a heat source)
7) Reassembled it all...
When machine is turned on at power point...
a) Detergent dispenser solenoid clicks on (normally would not do this)
b) Only 4 of the 6 available cycles buttons beep, and light up.
c) The "one touch start " does not work at all
d) The "end" cycle button does not work at all
e) There was a momentary "flash" behind circuit board When you say momentary flash, what do you mean?
Because I don't have a detailed wiring diagram ( have the one that came in a plastic sleeve in the base of the d/w) I could only visually check circuit:
Did not appear to see any burnt/loose/damaged capacitors etc. The continuity was okay with every one I "tested".
I did notice a blackened mark under the clear cover of a relay connected to the heater circuit and it didn't look right.
I exchanged the control board with that of a an almost identical model but the same reaction occurred except it also activated the "eco" button so I reinstalled original control board.
So, AJ, sorry for the lengthy story...this is why I was hoping to get a more detailed service manual to allow a lay person to trouble shoot the control board and other steps to get this fine old machine back on its legs again.