Ha! It's nice to see I'm not the only one with this problem. My WJD1457W is coming up to two years old and recently started doing this, intermittently, usually at 55 mins or 46 mins to go (on the cotton cycle). I too have checked all pipes and pump operation, everything seems AOK in that department.
The most annoying thing is that the machine is so clever, that even when you turn it off and turn it back on again, and try to do a drain only operation, it stubbornly refuses (not even powering the pump on), until you empty the water by gravity at floor level. This is a poor piece of software design in the controller - if there was a simple way of forcing it to drain, pulling the machine out of it's hole would be unnecessary!
Previous experiences with other machines (and dishwashers)have shown that the pressure switch which detects the water level, or pipe leading to it, are usually the culprits. I have had to clear lots of washing powder gunk from the bottom ends of these pipes in the past, when the symptom is usually overfilling, or continual draining. However, this machine has a wide diameter clear plastic pipe section ("sight glass") connected to the corrugated drum drain hose and the pipes to the pressure switches are connected *above* the highest water level, so there is less chance of blockage. I removed the pressure switches and blowed down the pipes and there didn't seem to be any blockage.
I delved further... there are two pressure switches, one of the conventional type with two or so "clicks" and mechanical 240V contacts which are used to ensure the heating element doesn't come on unless there is a minimum amount of water in there, and I think also controls the maximum fill level and determines when the drain pump should stop (I haven't drawn the wiring diagram yet so I'm not 100% sure, but it's very similar to my other Zanussi machine, see below).
The second pressure switch (the smaller one mounted on a small bracket by the controller) is more interesting. This is an electronic sensor which gives a continuous measurement of pressure as a variable-frequency waveform (you need a scope to see this but beware, the 5V suppy to this sensor is referenced to mains neutral, I think, so you need an isolation transformer). I didn't see a great deal of variation in this during normal operation, the period changing from ~22ms to ~25ms as the machine filled at the start of a cycle. This sensor internally has a variable inductance coil driven at ~40kHZ and uses a PIC micro to convert the signal from the coil into the FM output.
It seesm to me that there isn't very much decoupling on this little PCB and given the electrical noise from the heavy current motor signals which are bundled next to the wires to this sensor might be causing this micro to crash, but I can't prove that yet. I'm wondering whether the fact that the motor brushes are now more worn is introducing more electrical noise into this sensitive circuit? The machine is now interfering more with the radio in the kitchen (it was very bad when the machine was running in during the first few wash cycles).
I assume the continuous measurement of water level is needed for the software algorithm which works out how much water is soaked up and therefore how much laundry is in the machine? What I don't know is: which pressure switch is used by the software to decide if there is water present?
I'm very keen to get to the bottom of this (to keep the missus happy) so any snippets of information most gratefully received. I might try and have a moan at Zanussi, but I don't hold out much hope there. If it is using the second electronic sensor, I reckon some extra supply decoupling might help.
I also own an older Zanussi (1294?) which is very similar inside and has given almost faultless service after being rescued from the neighbours back garden in a half dismantled state. A quick rebuild and a new door seal and it was fine!
Colin Sinclair, November 2004
