How does a dishwasher know how much water is in it?

My neighbours dishwasher filled up so that when she opened the door there was a few inches of water ready to flood her kitchen floor.

I reckon it is a sensor fault. I dug about on the internet, and it suggests it is a flow meter that tells the machine how much water is in there. (

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could even be the same machine)

How does the flow meter tell how much water is in there?

or I am barking up the wrong tree?

Reply to
misterroy
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The ones I've fixed have a lever sensor which works on air in a pipe pressure they have a pipe from the area where the water collects at the bottom to a sensor which is usually round tucked away higher up in the machine. If the pipe gets blocked the machine over fills and/or doesn't empty correctly. Never seen a sensor fail it is usually a blocked pipe. Same idea in washing machines.

Reply to
Simon Templar

+1

Years ago had such a pipe blocked with soap gunge that caused the washing machine to over-fill. Cleaned out the pipe and all then OK.

Reply to
Chris Hogg

That is what I thought I was looking for, but after googling does not seem to be the case.

Reply to
misterroy

Time plus flow is volume.

Reply to
Fred

so how does it know when to stop measuring the flow?

Reply to
misterroy

It knows when it has turned the flow on and off.

Reply to
Fred

does it drain all the water into that big flat plastic bit at the side?

Reply to
misterroy

Dunno, I havent needed to do any work on my Bosch yet.

It does have one major quirk, it can be tricky to get it to start at times and quite often wont do two runs in a row, but does start fine the next day. But just a week ago did

3 runs in a row fine. Likely it?s a bad cap in the electronics board but I havent even got around to looking at that.
Reply to
Fred

Time multiplied by flow (rate). B-)

Might not need time as such. If the "flow meter" gives an output that coresponds to a given quantity of water having passed through. Say a pulse for each 10 ml. Count 100 pulses and you know that 1 l has passed.

It "knows" how much water it needs...

Reply to
Dave Liquorice

Washing machine "engineers" call them "pressure switches".

Reply to
Max Demian

Here is an excellent washing machine "pressure switch" video

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Secret Life of Machines. Wish he'd do an updated series.

Reply to
misterroy

I'd have thought there should be a level detector rather than a flow meter, as that would be too hit and miss in my view. One of the reasons I never got one is that so many who do have one have problems with them. In many cases the dishes need pre cleaning or the thing cannot cope so what is the point?Brian

Reply to
Brian Gaff (Sofa

I think the water depth in a dishwasher is not very much compared to a washing machine. Little depth means only a small pressure. I am inclined to agree that a pressure based water level sensor makes more sense, if you have enough depth...

Aye, they don't seem to be the most reliable of machines and there is all the faffing about loading, unloading, powders, rinse aid, salt etc. OK I think you can get "all in one" pods these days but I guess the salt requirement is still there.

And apart from having to pre-clean they send your drinks glasses all "frosted".

Reply to
Dave Liquorice

I always connect ours to the soft water supply and disconnect the *no salt* service.

Don't put any glass other than Pyrex/empty jars in a dishwasher!

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Reply to
Tim Lamb

Big Clive has a video tour of the innards of an Indesit washing machine at

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where he briefly points out the the fill level sensor at 1:17.

He also has a teardown of the ingenious digital sensor at

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Reply to
Mike Clarke

Excellent simple and informative presentation style. Thanks for the link.

Reply to
nothanks

See also recent dishwasher video(s) by the "Technology Connections" youtube channel

Probably difficult to capture the same vibe without Rex ...

Reply to
Andy Burns

More faffing about to maintain that. Not a problem here, lovely soft mains water since they switched the source to Burnhope reservior. No scale in kettle just a little bit of brown deposit that takes months to appear. Previously the supply was from an addit in limestone, that was a little hard, descale kettle once or twice a year of nearly pure white scale. St Albans, hard as nails, descale kettle every couple of months of scale in lots of pretty green and blue colours...

More faffing about hand washing your glasses when you've spnet lots of money an a machine that doesn't do what it's supposed to do...

Reply to
Dave Liquorice

Thank you. I've often wondered whether they have multiple switches or a transducer to allow for different filling levels.

Reply to
Max Demian

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