Miele G692 inlet drain error

[gt5500]

I am trying to fix my parents Melie G692, the engineer has been unable to diagnose the fault.
What happens is when a cycle is started the drain pump runs (and clears the water) then the inlet valve opens for 5 seconds or so and stops, it repeats this about 5 times (the inlet valve not the drain pump) and then the inlet drain fault led comes on.
So far I have tested the flow sensor reed switch using a magnet and it shows continuity when the magnet is applied, when fitted it shows fluctuating continuity when the inlet valve is open so I would say its working.
I have also blown gently into the pressure sensor hose and the switch clicks but I have not checked it for continuity. What should I check next? I wondering if it could be a jammed circulation pump?
Thanks

[electrofix]

its not an easy fault and does sound like a board failure

cant be flow valve as even if its not working it takes longer than 5 secs to stop the flow

cant be the wash or drain pump as these dont run during fill

could not be pressure sw as again it would take longer than 5 secs to fault out

my next step would be to either energise the valve or measure the voltage going to it. we need to make sure the vale is working ok. just be careful if you work with mains voltages

dave

[gt5500]

The fill valve appears to be working as water comes rushing in when it opens but it then shuts after 5 seconds or so. This repeats about 5 times before the error is displayed.
I am wondering if the reed switch may be closing but with high contact resistance. The engineer is convinced the flow meter wheel is at fault, obviously a very expensive part to replace as it’s part of the fill chamber. I’m not convinced, the wheel spins very fast when water is flowing and the reed switch does register it but without using a scope it’s impossible to say it’s registering the correct pulses.
I may try soldering a new reed in to eliminate that as a suspect.

[electrofix]

flow meters are cheap. you can get a reed sw for £2 or so and solder it in but i dont think its the problem

Dave

[gt5500]

OK thanks for your help, where should I look next? As I said the intake valve surely must be working as it switches on and off and water comes in at what would seem to be the normal rate.
What else is the machine checking for during the fill stage? Could it not be stop/starting because it isn’t getting the correct pulses from the flow meter?
​​​​​​

[electrofix]

I doubt it
from the dishwashers i have seen with dead flow meters. even with no pulses it flows in freely untill the timer realises and faults out. there is no reason for it to pulse

the only other possible explanation is a blockage creating pressure in a switch so it thinks its full, then the pressure subsides and it tries again

Its a long shot

Dave

also look at this
https://www.manualslib.com/manual/1052537/Miele-G-600-Series.html

[gt5500]

Yes I saw in the manual it says the heater level switch is connected in series to the fill valve so if it’s tripping it will stop the flow.
Having said that I have done some more reading and found several cases of the same symptoms which were solved by a new flow meter. Maybe it looks for flow to start when the valve opens and if it doesn’t see any it closes the valve and reopens and checks again?

[electrofix]

miele want £33 for the flow meter so i would solder in a reed sw

there are also at least 10 different variants of the G692 so i picked one at random

Dave

[gt5500]

Any idea what spec of Reed switch? Voltage, current rating? I work in an electronics company so may have something here but without dismantling the machine I’m not sure what type I want. Thanks for all the help.

[electrofix]

its only working on logic circuits so its not taking any current. think the one i use is good for 125v or so

its more a question of size as it needs to be small enough to go in

Dave

[gt5500]

Cool thanks, I think we have something suitable at work.

[gt5500]

OK so I changed the reed switch and there was no change. I metered out the reed switch whilst the fill valve was open and can read voltage so the metering wheel is definitely turning and triggering the switch.
I’ve also checked the circulation pump is turning freely, checked the circulation pump pressure switch clicks when I blow into it (hard). I metered out various solenoids and none were open or short circuit and also made sure the flood switch clicked in and out (I didn’t measure it but I believe a fault with that causes the drain pump to run continuously).
​​​​​​Don’t know what else to try, the engineer is convinced it’s the mixing chamber but the only moving parts are the ball valve and the metering wheel so not sure how it could be that? It doesn’t look blocked.
​

[electrofix]

well you could try one experiment if its possible

disconnect inlet valve pipe from mixing chamber, and see if you can re-arrange it to jet the water into a bowl or bucket. then try it to see what happens. if the water still spurts in 5 sec bursts then i dont think its the chamber but if it flow free with no probs then you know something is pressurizing and switching it off

Dave

[gt5500]

Good idea, I’ll give that a try

[gt5500]

So I finally got back there, I did your test albeit it slightly differently. I simply turned off the water at the mains isolator and ran the machine, you can hear the inlet valve open and then close again after 5 secs or so, the same as it does when the water is switched on.
This leads me to think it’s either something to do with the flow sensor (read switch already replaced and voltage can be measured when the water is flowing so seems to be working), the flow sensor circuit (again, voltage can be seen so not sure how it can be that) or the main board.
The engineer that visited is convinced its the flow sensor wheel, but I don’t see how it can be as a) it spins and b) when it’s spinning voltage flows through the reed switch.

[Author]

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