Neff S5456X2GB/42 keeps draining

[renMike]

Hello,

I’ve recently observed a problem with my Neff dishwasher (model #: S5456X2GB/42). This is a fairly old unit at 8 years, but it has been trouble free all that time.

The symptoms are that towards the end of the program it drains the machine and appears to not sense when the water has gone as it keeps on draining. This extended draining process carries on until the end of the program and beyond. It’s not known if there are any missing steps in the programe but the dishes seem to have a salty residue left on them and sometimes there is a white reside in the base of the machine. Left unchecked the drain cycle carries on indeninitly. To stop the program I need to force the reset and then turn it off. If I put it into test mode and check the error code I get E6 which I think is a Heating and Filling error, but I don’t know what to check next.

So far I have tried:
Cleaning the machine buy taking out the drain components in the base of the dishwasher.
Checked that the impeller is not blocked/clogged.
Removed the left hand side to examine the float mechanism controlling the water input. This was quite dirty and so was cleaned.
Checked the overflow sump (in base on left hand side) to see if it contained any water and so could be requesting the machine continue to drain. It was found to be empty.
Just in case I’d mistook the sump for something else i’ve tilted the machine forwards and backwards to drain any water out (only water from the pipe work exited the machine).
Checked the switches on the left hand side to listen if they audibly clicked when activated. They did.
Checked the switches on the left hand side to see if they broke/made a circuit when activated. They did.
Watched the machine run without the left hand panel on and visibly saw the water enter the machine. In doing so it triggered the switches to presumably avoid flooding the machine.
During the running of the machine I manually activated the float mechanism and it successfully stopped the input of water for the time it was activated.
Removed the bottom pannel to see if anything obvious was wrong there. Couldn’t see anything obvious.
Removed the right hand panel to see what was there. I was able to observer the motor running at this stage.
Removed the circuit board to look for burnt spots, but none were visible.
Searched the Neff, Bosch and Seimens web sites for clues, wiring diagrams, etc. to help but nothing has yet turned up.

I took photos at most of these steps in case they can help diagnose the problem.

My current theory is that there is a switch/sensor/sender somewhere in the drain that is not activating when the machine is dry but I can’t find it.

Does anyone have any other theories as to what might be causing the problem or suggestions as to what i might test as i’m now stumped.

Thanks,

Mike

[Martin]

Re: Neff S5456X2GB/42 keeps draining

renMike wrote:If I put it into test mode and check the error code I get E6 which I think is a Heating and Filling error, but I don’t know what to check next.

Well the obvious question for us to ask of you Mike then is:

Is it heating?

[renMike]

Re: Neff S5456X2GB/42 keeps draining

I think so. I’m not getting the full steam effect I used to get when it was working correctly, but then I don’t know if its got that far in the cysle.
Is there a definitive way to test?

[Martin]

Neff S5456X2GB/42 keeps draining

renMike wrote:Is there a definitive way to test?

Towards the final part of the cycle i.e the final rinse, it heats up to its maximum temperature before draining out and therefore should be, at that point, well hot and steamy!…..I suspect that is not happening. 😉

Conclusion : Heater needs replacing. 🙁

[renMike]

Re: Neff S5456X2GB/42 keeps draining

Is the a way to test for sure? If seen other models have insructions for either the control board or heater itself to test continuity, but I can’t find any for my model.
Also, If the heater isn’t working would that normally keep the pump running?

[Martin]

Re: Neff S5456X2GB/42 keeps draining

renMike wrote:Is the a way to test for sure?

Well if it wasn’t getting hot during the wash cycle that would be very obvious. I am more than confident from your statements so far that it isn’t heating. You’ve checked the PCB and found nothing untoward there so that also supports my assumptions. The heater can be easily checked with a multimeter anyway should you wish. Disconnect from the mains first of course. 😀

renMike wrote:lso, If the heater isn’t working would that normally keep the pump running?

Can’t rule that out at this stage and a faulty PCB cannot be ruled out either but first things first I would suggest. 😉

[renMike]

Re: Neff S5456X2GB/42 keeps draining

Ok, I’ve just sent it through a normal ‘eco’ programme which should take 85 minutes (according to the display). At about 50 mins through the programme I believe that it started to drain and didn’t stop. With 30 minutes left on the clock I opened the door and heard the drain ‘sucking air’. The inside of the machine was very warm but not steamy. The programme was cancelled at this point.

Reading testing documentation for other Bosch machines I note that there is a test mode you can put it in which runs short cycles of each stage to test them. Is this an open for my model? If there is and I can access it then I think that would prove if the machine was heating, filling, draining, etc.

Alternatively, would you mind posting instructions or pointing me at a link containg instructions so I can complete that test?

Thanks,

Mike

[renMike]

Re: Neff S5456X2GB/42 keeps draining

Is there a switch or sender to tell the machine when it has drained all the water or is it on a timer?

[Martin]

Re: Neff S5456X2GB/42 keeps draining

renMike wrote:Is there a switch or sender to tell the machine when it has drained all the water or is it on a timer?

The water level switch is the one you first mentioned in your opening post: –

renMike wrote:Checked the switches on the left hand side to listen if they audibly clicked when activated. They did.
Checked the switches on the left hand side to see if they broke/made a circuit when activated. They did.

The switch has 2 positions, empty and full. On receiving an empty circuit the control board drains for 60 seconds and then switches on to the next stage of the process. In this case to OFF.

[renMike]

Re: Neff S5456X2GB/42 keeps draining

Doh!
I know the swtch is working as I can manually acctuate it and the er flow stops/starts.
I guess that means the control board has gone (without visible damage). Is there a way to test this via continuity or current measurement?

[Martin]

Re: Neff S5456X2GB/42 keeps draining

I can’t help thinking you know that for some reason I’m not getting the full picture on this fault. I’ve read through your previous posts and as a result am convinced I’m not getting the full story here. 😕

So let me roll it back a pace to this point: –

renMike wrote:With 30 minutes left on the clock I opened the door and heard the drain ‘sucking air’. The inside of the machine was very warm but not steamy. The programme was cancelled at this point.

“sucking air” means to me that you either could hear the circulating pump stopping as you opened the door OR the drain pump pumping…..whichever I cannot determine from this remote location.

“The programme was cancelled at this point”…how? By you or at the point when you opened the door it stopped….or did it NOT STOP when you opened the door? The latter part of my questioning very important by the way. 🙂

[renMike]

Re: Neff S5456X2GB/42 keeps draining

Martin,

Thanks for going back over the trail. I too think I am missing something obvious here, but unlike you I don’t have a wealth of experience to draw upon.

To answer your questions:
The “sucking air” sound was first noticeable with the door closed and the machine apparently mid programme. I was initially curious why the same noise was comming from the machine for what seemed too long a period and so opened the door. The sound continued even when the door was open. Since the machine doesn’t actually suck the water out (I may be wrong here) I’m presumming that the sucking sound was actually the impeller spinning in a shallow pool of water(?).

The programme being cancelled was manually by me via the Auto + 35 degree key combo.
To speciffically answer your latter question, it did not stop with the door open untill I manually cencelled it.

Since the last post I have further investigated what I now know to be an “Air Pressure Switch”. This is a round device under the inlet reservoir with a protruding peg that pushes against a horizontal blue bar. This device apparently controls how much water is in the machine(?). I knew that the switch it [blue bar] operated was operational since I ran a continuity test on it a week or so ago, but at that time I disassembled, cleaned and reassembled the whole pressure chamber assembly and may have either missed some gunk or damaged the sensor in the process. So may aim tonight was to get the machine into the fail state (e.g. “sucking air” state) and try to manually accutate the switch. The result of this test is that this does not appear to be the problem as although I could hear the switch clicking it made no difference to the machine.

One point of potential interest is that I initially could not get the fail state tonight since I had selected the Quick Rinse programme and this finished normally. I then tried the 35 degree programme and this failed as described. I guess that the Quick Rinse programme is not doing something that the other programmes are doing. Any ideas what that something could be and does it help diagnose my problem?

I really appreciate your perserverance in this matter as my other half is getting a bit upset at the prolonged absence of said machine and if I can get it fixed rather than having to buy a replacement I’d feel a lot better. If there are any tests or further descriptions I can provide to help then please let me know.

[Martin]

Re: Neff S5456X2GB/42 keeps draining

Quick Rinse (a.k.a Pre-rinse or Pre-soak)is exactly that, just a cold water rinse to flush the plates and leave them cold and wet. The other programmes require HEAT at some point during their cycle as they are all complete wash cycles.

As far as the “sucking noises” are concerned, I have now realised you refer to the drain pump. If that continues with the door open then that indicates that the anti-flood device is in operation. (That’s the red rod float device operated microswitch by the way). As a rule that means the baseplate is flooded to a point where the polystyrene lifts the red rod, thus activating the drain pump (with or without the door open and machine switched on). If however the anti-flood device hasn’t been activated and yet the machine still behaves in this way then as a rule it is a failing of the main PCB.

HTH?

[renMike]

Re: Neff S5456X2GB/42 keeps draining

It probably does help. I’ve already checked the sump and it is dry. I’ve manually tried actuating the anti-flood device (red rod) and it makes no difference once the unit is in its fault state. To complete the tests I also tilted the machine forwards (and backwards) but little to no water came out. I think that the only water that did come out was the residual from the drain.
So yes, your diagnosis does kind of help as it points the the main PCB.

Is there any conclusive test I can conduct to prove this?

[Author]

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