Bosch SMS50T22GB/34 – Flashing Check Water Light on power on

[Dourn]

Hi all.
I’ve read through every single topic on this dishwasher and the infamous flashing check-water light, but can’t find something that is identical to the issue I have.

Dishwasher starter not draining properly some months ago – leaving water behind in tray.
And then the Check Water light started flashing.

What happens is this: you turn on the power, it starts going through it’s “start up routine” and you’ll hear a few clicks, then you’ll hear the drain spin 4 times (and I verified that the impeller was turning by removing it and seeing it turn whilst still plugged in) and then the check water light starts flashing.
You can’t even get to the point where you start a cycle.

I cleaned out the sump, that didn’t help.
The impeller wasn’t broken or blocked.
But I decided to bite the bullet and replace the drain pump (part no 00620774).
Didn’t help.
I checked that the drain cover over the impeller is fitted.

There’s no water in the bottom, so the float switch hasn’t activated.
I took out the water inlet assembly (also known as a Water Labyrinth) – I could see it had a lot of food residue in it, so I cleaned that all out.
Still not working.

If you push the start button straight after pushing power, you get an additional humming sound (which I think is the main motor).

So I’m a bit stuck what part to test/replace next.
I was going to apply 230v to the water inlet solenoid just to check if that’s working – although given this happens before a cycle starts, I wouldn’t expect that solenoid to be used at all.

I was hoping to find out what the dishwasher does on power on, i.e. what components does it power up or test?
Or see if anyone else has any other ideas.

Thanks in advance.
Dan.

[electrofix]

all the flashing light means is I have a fault, problem is we dont know what

if it was a water inlet problem it would not flash so that rules that out

the timer unit uses pump current to determine if there is water in there. Have you tried mopping out the water and see if it fills

Dave

[Dourn]

Thanks, Dave.

Yup, I’ve tried cleaning out all the water (from the sump at bottom, where the drain pump is) and I’ve also tried it with water in there.
Same thing happens in both cases: the drain pump spins 4 times (you can hear it, it’s like 4 pulses, rather than a continual spin).

There’s water in the water softener unit (I never emptied that) but none in the water inlet assembly (water labyrinth).
The drain pipe is clear all the way from the drain pump to the actual drain.

The unit was off for a good 3 months with no power, so it’s not a case of it being something remembered whilst having power.
I know that these units will attempt to restart a programme when interrupted, even if power is disabled e.g. during a power cut.
But I’m not sure if that happens over a long power outage (i.e. is it stored in a short term memory, or written to memory in the unit that retinas that state even after a long power outage).

What I’m saying is that I’m not sure when I power it on if it is attempting to restart the last programme, or just going through a normal power on check.

Dan.

[electrofix]

to be sure you need to turn on and cancell the programme. it will then run a pump out sequence

you can then turn off and set another programme and see what happens

Dave

[Dourn]

Yeah, that’s what I figured – but the only way to cancel a program on this model is to hold the start button for 3 secs, and it ignores that, and still runs the startup sequence which ends with the flashing light. My next step was to go look at the main control module and see if there’s any way to do a reset.

-Dan

[electrofix]

there is no way as far as i know of resetting from the module

Dave

[kaibart]

If the flashing check water light comes on there are a few things it can be the contact Reed switch, the drain valve or the heat pump

[Author]

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