Water level sensors in dishwashers

According to my Haynes Dishwasher Manual, there are several possible ways of implementing level control. The principal ones seem to be pressure switches (similar to washing machine but with a lower level of trapped air) or float switches.

The descriptions are fairly generic, and is doesn't say which makes and models use a particular system - but the above just might provide a clue as to what to look for.

There's a video covering this topic:

In message , Tim Watts writes

Our old AEG one would sometimes do this. A 'fix' (of variable amount of time - could be months) was to tip it over to one side. some water would run out and it was fine after that

Have a look at the exploded diagram on the Bosch spares website.

Dishwashers I've serviced work the same way.

Common problem is a build up of some type of grease which the dishwasher detergent doesn't dissolve, which blocks the pipework. Clean the machine thoroughly (filter out, and clean the well with a washing up brush and a _little_ washing up liquid). This may clear the entrance to the pressure tube. If it does, run a cleaning cycle with a dishwasher cleaner. Also, in future, a couple of drips of washing up liquid in each wash seems to stop this grease building up.

The failure is usually that the the pressure pipe has got blocked and the sensor is feeding back that there's water in the machine when there isn't.

You haven't said why you think it's the pressure sensor. If you don't have some error code which tells you this, the other option is the machine has leak detection which has triggered. This is usally a large tray under the whole bottom of the machine, which has a float which trips if water leaks into the tray. Machine won;t do anything different until the leak detection tray has been emptied out and the float drops back.

On Wednesday 30 October 2013 09:49 Roger Mills wrote in uk.d-i-y:

Haynes do a dishwasher manual? I really should get that - even if out of interest...

I hadn't thought of float switches... Ta muchly - very interesting!

On Wednesday 30 October 2013 20:51 Andrew Gabriel wrote in uk.d-i-y:

Seems reasonable...

The pump runs continuously. The drain is not blocked because if I throw in a bowl of hot water, it is emptied out from the machine efficiently = but the pump does not stop - which is why I thought "level sensor".

However your suggestion of a leak tray is interesting - I can look at the Bosch Supplies website that has exploded diagrams and see if it has one on this model.

Long story short - it is problaby uneconomic to me (very time starved this and next month - you would not believe it!) but I was interested anyway...

My old AEG was the same, I think there was a small weep on one if the seals where the heater was fitted, and it dripped into a tray underneath, then when it was full, a float switch triggered and stopped it working, and ran the pump all the time.

Another alternative: On my parents machine, many years ago, leakage was detected by a piece of sponge. If the sponge got wet, it softened and released the microswitch. In their case, it slowly indented over the years and went into leak mode despite being dry - reversing the sponge solved the problem.

SteveW

On Wednesday 30 October 2013 12:08 chris French wrote in uk.d-i-y:

Ah - that sounds like the "leak tray" that Andrew mentioned a couple of posts back - I *could* certainly try that!

I *think* my Bosch DW has a "washing machine" type one. There is a float switch to sense for leakage into the tray underneath the whole lot which then trips the water inlet valve.

On Wednesday 30 October 2013 10:54 Richard wrote in uk.d-i-y:

Wow - suddenly I am inspired to have a look!

It's not too hard to pull out and get the side panel off (I thought it would be a horrible dissassembly).

Many many thanks!

On these models there's a float switch in the base which triggers this. On mine it was due to a slight weep on the inlet flange that drips down into the base (which is effectively a big tray) filling it up over the course of a couple of years.

If it's this then just emptying out base (and curing whatever's filling it up) solves this rapidly!

Yes, in addition to the car manuals they do a number of more general manuals - caravans, dishwashers, washing machines, computers(!), Home Extensions, loft Conversions, etc.

The dishwasher manual is necessarily generic rather than specific to a particular make and model, but it provides quite a few clues of what to look for - as well as providing a lot of stuff (which no-one here needs!) about general plumbing and electrical supplies.

I bought it when my son had a problem with his dishwasher, but never managed to get sufficient access to the machine to be able to sort it.

On an Ikea/Whirlpool dishwasher, I have seen the leak tray trip due to a bit of cutlery in the basket getting trapped in the door seal and causing enough water to leak into the tray that way. However, I've also seen it happen due to split pipe.

And they do a manual on how to have sex in or on a car.

Dunno. There is apparently an Owners Workshop Manual telling you how to maintain a MAN! I don't know whether that includes DIY regeneration. If not, perhaps you'd like to offer to write one?

It was not a question.

Blimey! Yes, sorry, I did misread your previous post.