Bosch Dishwasher - Intermittent Leak

southsaxon · 16 Dec 2012

Bosch dishwasher SGS43T52GB

This machine is 6 years old and has always worked perfectly. My Wife is meticulous in keeping it clean, cleaning the filter regularly etc.. The machine has never been moved from its original location and has always been totally reliable.

However, out of the blue, it recently leaked quite badly through the bottom of the door when on the pre-wash. Water just poured out. Fortunately I was close by and was able to turn the machine off.

We checked the filters and the impeller down in the floor of the machine (which was not jammed or damaged) and all seemed to be ok, and so did the door seals. Neither of the spray arms appeared cracked or damaged.

We tried the dishwasher again and it worked fine for a couple of weeks, with no leakage at all, and then, just as our confidence was returning, the same problem reoccurred - bad leaking through the door on the pre-wash.

We re-checked everything as before with the addition, this time, of the domed float cover which seems to be able to move freely up and down.

Neither my wife or I have changed the way we stack items in the machine nor have we any new or overly large items that might be causing an obstruction.

Is the leak likely to be a faulty safety cut off switch under the float? If so, how do I get to it to replace it as, having taken off the front kick plate, I can’t even see the switch, let alone get to it.

Or, alternatively, is there another likely reason for the leak?

JohnD · 16 Dec 2012

had somebody just opened the door?

was the machine very foamy, e.g. traces of washing up liquid or other detergent?

IIRC the water level sensor is inside the left-hand door as you look at it, connected with an air tube to the water.

If you put the model number into the Bosch Spares website, you can see exploded diagrams which are very useful for seeing how it is put together.

http://www.bosch-home.co.uk/store/spareparts/search

southsaxon · 16 Dec 2012

Thanks John D

Sorry, I should have said in my original post, the door was firmly closed, the machine won't turn on if not, and no one was fiddling with it

No sign of excessive suds.

I’d already checked the exploded parts list diagram and the only things that appear to be in the door relate to the detergent dispenser and the trigger switch for detecting that the door is open.

The "Safety System", which I take to include the water level float and trigger switch, is built into and under the floor of the washing chamber, about in the middle. The part doesn't look too expensive to buy but I can't work out how to get to it unless I take a side panel off and come in from the side or the back - it’s a free standing machine BTW.

We reckon it started leaking, on each occasion, within 10 mins of starting the pre-wash, perhaps near the end of the pre-wash cycle - too early for a pressure build up I'd have thought.

JohnD · 16 Dec 2012

I don't know why I said "the left-hand door"

I meant "the left-hand side" but in your case it seems not to be right. I think the depth switch is operated by air pressure going up a tube, rather than by a float.

southsaxon · 16 Dec 2012

Thanks John D

So is the entrance to the tube you mention, something to do with the circular vent thingy (about an inch diameter)about 10 inches up the left hand (as you look at it) side wall appx in the middle?

Or is it under the small mushroom thingy in the middle of the floor almost under the bottom spray arm.?

Any ideas?

JohnD · 16 Dec 2012

sorry I don't know

southsaxon · 16 Dec 2012

Ok John D, thanks any way.

zipper · 16 Dec 2012

Leaks from the door are commonly caused by split spray arms or bad door seals, but if you have checked these out then it's got to be something else.
Overfilling can be caused by a faulty flowmeter http://www.espares.co.uk/parts?k=424099 or a partially jammed open inlet valve (very unlikely on this model since it has a dual valve). If the machine overfills the float on the safety switch should rise, cut voltage to the inlet valves, & activate the drain pump. The same will happen if water leaks onto the baseplate. You can check the safety switch by manually lifting the float. If the drain pump kicks in & empties any remaining water then it is working as it should. To get at the flowmeter the LH side panel needs to be removed. When replacing it make sure the new one is fitted the right way round (marked with an arrow showing direction of flow).

southsaxon · 17 Dec 2012

Thanks for your input zipper.

When I click on your link to the flow meter I get the impeller jug part?

Can you give me the correct part number for the flow meter so I can do a search for it and look for it on the exploded parts diagram for SGS43T52 that I’ve downloaded.

I was assuming that it was part number 490618 (http://www.espares.co.uk/parts?k=490618) that was the key but are you saying the flow meter is a different part?

How do I check the float is working ok ‘cos when I open the door the machine stops. Do I disconnect this switch in the door?

Thanks again for your help.

zipper · 17 Dec 2012

"Impellor jug" is Bosch terminology for a flowmeter.
Part number 490618 the safety switch assembly...not the flowmeter.
The flowmeter is item 0515 on page 5 of the contructional drawings. It has p/n 424099 & is located under the braketank on the LH side. Just follow the inlet hose you can't miss it. If you lift the float (with the door open & the power on) the safety switch should activate the drain pump. Alternatively you could check the micro-switch in the base with a multimeter.

southsaxon · 17 Dec 2012

zipper thanks for all of this info..

So there is no way of checking the flowmeter (0515), just a case of replacing it just in case it’s faulty?

Sorry to be a bit slow, but are you saying that when checking the safety switch, by manually lifting the float, it will activate the pump even with the door open so overriding the switch in the door which normally shuts the machine down when the door is open?

Finally, what’s the best way of getting to the microswitch to test it with the multimeter? There is only the smallest of holes at the front after taking the kick plate off.

Thanks for being patient with me on this, I really appreciate it.

zipper · 17 Dec 2012

You can blow through it & it'll make a really cool whizzing noise....

But there is no easy way to test it...at less than £20 for a new one you may as well just throw it in the bin & fit a new one.
Yes the drain pump should kick in when the float is lifted, which verifies the antiflood switch functions as it should.

southsaxon · 18 Dec 2012

Thanks zipper.

I'll take the side of now and see what I find.

southsaxon · 18 Dec 2012

zipper, before taking the l/h side off I tested the float. It works but only when there is more than an inch (25mm) in the base.

So when I chuck a load of water in the float lifts, the pump kicks in and the water drops to about an inch and then it stops. So there is always appx an inch of water in the base. Is this as it should be?

zipper · 18 Dec 2012

Yes...The primary function of this device is to prevent flooding your kitchen when there is an internal leak (water on the baseplate). But it will also safeguard against overfill within limits. Once the water level in the machine is low enough to reset the microswitch in the base it will stop pumping out. It will not empty the machine completely, this only happens when there is water on the baseplate. But if you manually lift the float it will pump out everything.

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Bosch Dishwasher - Intermittent Leak

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