Neff dishwasher filling with scarcely a trickle. ?Aquastop?

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(This is my first post in any forum anywhere so please forgive me if I get it wrong.)

I have a 17 year old built in Neff dishwasher (S4152). It was worked flawlessly till now. I am reluctant to junk it for all sorts of reasons and don't want to be given that advice by a service engineer.

Now, it almost fails to fill. Water trickles in and no more. However if I leave it, the dishwasher eventually fills and goes on to complete a rinse cycle normally. I am reluctant to try a full wash cycle in case the heater comes on before there is sufficient water in the machine.

There is no water in the sump and never has been. The sump looks as good as the day it was made. Therefore I do not think that a leak has caused the machine to stop filling. Reading the forums, it therefore seemed that it would either be some kind of blockage or else an inlet valve problem, either on the machine or on the aquastop itself. The machine empties correctly when first switched on and so the waste pipe would seem not to be blocked.

I've tried investigating the aquastop (more of that later if necessary) but the most significant finding is one I haven't been able to repeat, try as I might. That is, I tried unscrewing the salt container lid and found that the water inside was at a modest pressure in the sense that some water came out (maybe half a cupful). I have never used the salt container because I live in a soft water area where salt is never needed and so I don't know if that slight pressure is normal. The level in the salt container appeared to be lower by more than half a cupful for reasons I don't understand. After doing that, the machine filled rapidly (ie as normal) until the salt container appeared to be full again and then the flow reduced to a trickle again. I don't know why I can't repeat this. I've tried spooning some water out of the salt container but that does not reproduce the effect. Perhaps I need to suck more water out of the salt container in order to trigger the effect. Or perhaps I had done something else that I was not aware of and so can't remember. In view of this I feel that the aquastop must be ok but wish I could reproduce the salt container effect in order to be sure.

So, does anyone have any idea what's going on here, please? Thanks for being patient and getting this far!
 
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leave the salt container alone , not sure why that attracts your attention
the fill valve is possibly the problem
try putting a bowl of water in the machine while off, then switch on to start the cycle , see if it empties and goes on to the next part of the cycle - cold fill - if so i reckon that is it , if not then you have another prob and more investigating required
also check silly things like is the water supply actually ON
is the supply pipe kinked or blocked at the inlet cap
 
Thanks for your interest, cakeman.

The salt container attracted my attention because of that one time when I noticed that it was only two thirds full - don't know why that was. On that occasion starting the the cycle from the beginning resulted in normal flow of water through the aquastop into the machine (actually directly into the salt container judging by what I could see through the translucent container wall) until the container filled up. Then the flow reduced to a trickle. The fact that normal flow could occur through the aquastop at all, even if only on that one occasion, was what drew my attention away from the aquastop and towards the salt container. I thought it could also be some control (eg pressure control or something) that could have been disabled when the salt container was not full but reapplied when the salt container had filled up. Surely it would be too much of a coincidence to conclude that the salt container has nothing to do with it when it being 2/3 full leads to temporary normal flow until the container is full, and then the flow reduces to a trickle.

In answer to your question, when I put a bowlful of water in the machine and start the cycle, the machine empties and then does go on to the next part of the cycle but only with that trickle of water. If I leave it filling, it eventually fills to its normal level and goes on to the rest of the rinse cycle.

Thanks for the reminder about the water supply being on, but yes, it is! At least it was when I did all this. I've since disconnected the aquastop from the water supply but have not looked into that any more yet. I don't know whether the supply pipe is kinked at the inlet cap because I haven't taken the (built in) machine out yet. However the supply pipe has not been moved for 17 years and so should not be kinked now.

Will there definitely be an inlet valve inside the machine as well as the aquastop valve outside?

I think before I go further I have to try to reproduce the salt container phenomenon, perhaps by sucking more water out of the container first.
 
is good to see good detailed postings on forums . good stuff

i think your right about all the basics but i do suggest a more thorough test of the inlet valve is the 1st call
 
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Thanks. I'm notorious for being a detail person! I can't help it!

Is the inlet valve usually easily accessible if I take the machine out from where it's built in?

I'll see what I can find out tomorrow. I have questions about the aquastop too but I'll keep them till I've found out a bit more. I'm not convinced that the problem is anything to do with the aquastop but it may well have to do with the inlet valve.
 
fasten the water fill without the aqua stop . see what next

the water fill solenoid has 2 small wires attached and will be located inside the machine adjacent to where you screw in the cold fill pipe

HTH
 
Not much progress I'm afraid (other commitments).

However I did try to repeat the finding of the salt container filling up rapidly (ie normall) until full and then the flow rate slowing instantly to a trickle. I sucked about half the water out of the salt container and tried the rinse cycle. This time there was no repeat of the temporary rapid fill but the salt container and then the main machine did eventually fill up, all at the trickle rate, and go on to complete the rinse cycle.

One thing I did notice was that there was some reddish-brown debris stirred up when I sucked the water out of the salt container. Not what you would call sludge but more like what you'd get if you disturbed the water at the bottom of a cold water storage tank, say.

Taking all this into account, I'd guess that you're right and that the first port of call is the inlet valve (possibly blocked, possibly just faulty). However I can't rule out that it's the pressure sensor that is shutting off the aquastop. I now don't think it's likely that the aquastop itself is faulty. Nor do I think that it's anything directly to do with the salt container (although I wonder if that could have something to do with it if it is after all an over-pressure effect).

It would be really useful to my understanding of the workings of the dishwasher if you could be bothered indicating to me the "circuit diagram" of the water flow in the machine (eg inlet service pipe->aquastop->inlet valve->....where?. For instance does the water then go through the salt container to flush it out? Or directly into the machine via the opening halfway up the side?

Thanks for your interest.
 
The aquastop is the inlet valve,and will be a grey box attatched to your water supply.
 
Thanks, assuhors. Are you saying that the aquastop is the only inlet valve, or is there also an inlet valve inside the machine itself?

Because it was one of the easier things to do (before I started this thread) and seemed to be relevant to the machine not filling, I took the cover off to reveal:

a translucent cover containing I presume the valve solenoid/motor with a cable from the dishwasher entering it; and
what looks to me like some kind of pressure control (a circular plastic housing with a black ?diaphragm in the middle and a clear plastic hose (~5mm) connected to it from the dishwasher.

The cover containing the solenoid/motor for the valve looks as though it is filled with yellow fluid. At first I thought this was dirty water leaked out from the waste pipe somehow although I had no idea why it would be that fairly bright yellow colour. I now suspect that it is grease because when I begin to lever the cover off, there is a "bubble" effect visible through the cover but no visible leak of water.

  • Can I simply lever off the cover to check if there is voltage at the solenoid/motor and whether it seems to be operational? (It hums gently when the machine is trying to fill and so must be getting at least some power.)
    Could the pressure control be faulty?
    What pressure is it measuring anyway?

By the way, the aquastop has no manufacturer's identification and so I suspect it's "made by" Neff.
 
See above: When I say I took the cover off, I mean the cover of the aquastop of course.
 
The aquastop is the only valve that controls the fill.The other items within that box are the safety shut down of the valve via the small clear hose.
 
Sorry to push you on this, "assuhors", but are you saying that the only two things left which could still be causing the machine not to fill are a) the fill valve in the aquastop being faulty or b) the pressure switch in the aquastop being either faulty or being kept off by some over- or under-pressure somewhere? (I think I've eliminated the other two things I could think of (the controller and the float switch in the sump) from the investigation. They're both ok.)

The reason I'm pressing you on this is that I understood "cakeman" to be saying that there is an inlet valve inside the machine as well. He says "the water fill solenoid has 2 small wires attached and will be located inside the machine adjacent to where you screw in the cold fill pipe".

(I'm not trying to prove someone right and someone wrong - just trying to understand this fault!)

Are all machines similar in that respect? Mine is an old Neff (S4152), 17 years old.
 
If you have an aquastop you don't have another fill valve inside.The safety shut down on the valve won't impede the flow.To replace the aquastop is quite a fiddle,but the most likely cause of your problem.
 
I just remembered that I could look up the exploded parts diagram on http://bshappliancecare.com/Neff/neffspares.html to check for valves. A bit hard to follow. There are a couple of valves mentioned but sure enough none seems to be an inlet valve (other than the aquastop).

What I don't understand is what the safety shut down on the aquastop valve is for if it's not to impede the flow (when necessary), my point being that perhaps I have fault conditions somewhere else in the machine that are making it necessary to shut down the valve and that maybe that's why my machine will only fill at a very slow rate.
 
The safety part of the valve shuts the valve down completely.I have changed many of these valves over the years mostly for the fault you are describing.
 

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