Neff Dishwasher fill problem

[RickT]

Model is S5456X1GB/12 integrated. When filling, the water fills the heat exchanger as normal, draining in to the pressure chamber. The water then floods out of the top of the pressure chamber.The red float is rising up and down with the pressure fluctuations with the usual thumping of the inlet valve and pump switching on and off. I have removed and checked the short hose to the sump. Replaced the pressure chamber with a cleaned second hand one. Removed sump filters. Checked tub venting. Still have the same fault. Have noticed the top left hand corner of the heat exchange is gunged up, but have seen this many times and has caused no problems. Does anyone know if these heat exchangers (215761) can cause this problem?
Cheers Rick

[RickT]

Re: Neff Dishwasher fill problem

:haier:

[Martin]

Re: Neff Dishwasher fill problem

RickT wrote:Does anyone know if these heat exchangers (215761) can cause this problem?

I don’t think so no, the only time the heat exchanger would need replacing is when that drain vent valve gets totally bunged up and leaks out the top.

The filling on these machines is complex to say the least. The electronics measure the time between when the inlet valve opens and the level switch is activated around that point in time the circulating pump should fire up whilst the heat exchanger continues to drain into the tub.

So, question: At what point in that filling process does the circulating pump run?

[RickT]

Re: Neff Dishwasher fill problem

Thanks for the reply Martin. As far as I can remember, as soon as the water starts to spill into the pressure chamber it gluggs away and small amounts start to leak out of the top. I’m not sure when the wash pump kicks in but I would say the timing seemed no different to usual.

[Martin]

Re: Neff Dishwasher fill problem

RickT wrote: as soon as the water starts to spill into the pressure chamber it gluggs away and small amounts start to leak out of the top.

It then has to be a restricted flow problem through the pressure chamber and transfer pipe, got to be. The moment the water starts to flow if you should happen to open the door will it drain into the tub without spilling?

[RickT]

Re: Neff Dishwasher fill problem

I’ve tried it with the door latch tripped opened, in case it was a venting problem. I have removed the short pipe and cleaned, although it wasn’t clogged. Checked the pipe connection in the sump. Could the black insert in the pressure chamber be causing a problem. I know other models don’t have this fitted!

[Martin]

Re: Neff Dishwasher fill problem

RickT wrote:Could the black insert in the pressure chamber be causing a problem. I know other models don’t have this fitted!

Hmmmmm?….That’s true! TBH I’ve never given it a thought until you mentioned it and I’m not sure it’s purpose???

I carry a 263186 Pressure Chamber as van stock without that black insert and I’m certain you could fit one of those OK and see what effect it has in curing the problem. 💡

[RickT]

Re: Neff Dishwasher fill problem

Returned today to machine and fitted 263186 which also had the rubber gasket fitted along the top. Result was pretty much the same except the water was now back feeding up to the top vent hole on the heat exchanger. :bang:

[nomadPaul]

That pressure chamber is the wrong one. you need a 497570.

It certainly sounds like a blockage in the pressure chamber/ribbed fill hose .

Once the matrix fills up and overflows into the pressure chamber , the microswitch arm should pop out and then this dumps the rest of the water from the matrix into the sump. The circulating motor should kick in after the approx the top 6 – 8 inches of water has left the matrix.

[RickT]

Re: Neff Dishwasher fill problem

Fitted 263186 just to see if machine behaved any differently to the original pressure chamber. Totally stumped me , this one. Pressure chamber cleaned, sump tube cleaned, tub vent clear.

[Martin]

Re: Neff Dishwasher fill problem

I think you have to ascertain at what point the circulating pump kicks in during the matrix draining process. As that enables fast draining into the sump and less chance of water backing up as it were.

But nevertheless the water syphoning out from the heat exchanger into the tub is a slow process for both the pressure chamber and transfer pipe to easily cope with. It’s not exactly a raging torrent of water after all said and done!

[RickT]

Re: Neff Dishwasher fill problem

Thanks again Martin. The water starts to leak out within 5-10 seconds from the spill over. Approx how long is it between the initial spill and when the wash pump kicks in? Just a stab in the dark here but does the water softener pull some of the water in at this stage to divert some of the pressure?

[Martin]

Re: Neff Dishwasher fill problem

RickT wrote:The water starts to leak out within 5-10 seconds from the spill over.

If it spills over the air gap in 5 to 10 seconds and the safety float jumps up and down activating the drain pump during that time period then it can only be due a a restriction of some sort into the tub (sump).

RickT wrote:approx how long is it between the initial spill and when the wash pump kicks in?

I’ve never timed it but I guess the norm to be around 10-15 seconds maybe?

RickT wrote:Just a stab in the dark here but does the water softener pull some of the water in at this stage to divert some of the pressure?

Well do bear in mind that the water enters the heat exchanger matrix via the water softener system anyway.(softened water enters on every fill) And there is no “pressure” involved in the gravity effect the syphoning action from the matrix gives in the direction of the pressure chamber.

Now, just as a test if you like, you could always take the transfer pipe off at the sump end and direct it, out the front panel, toward a shallow bowl. Then fire up the filling process and see if all the water that cascades down from the matrix flows unhindered into the bowl…! 💡

[RickT]

Re: Neff Dishwasher fill problem

Now why didn’t I think of that 😳 I’ll give that a try. Thanks for your help Martin. I’ll report back when I solve this mystery 😀

[leavemetogetonwithit]

Re: Neff Dishwasher fill problem

That’s a good idea but you could save yourself getting the electrics wet by simply tricking the door interlock and observing what happens in the sump with the filters and baskets and spray arms out of the way.
I remember a very similar situation on a pre-Lux AEG more than ten years back, to which I never found the cause.
Mike.

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