Bosch Dishwasher - not enough water

Hi all,

Dishwasher is playing up. Makes all the appropriate noises but only a light splash of water comes out of the bottom spray arm. Remove the filters and there is not much water there. If you manually add a couple of litres, regular spray operation returns, so it's clearly underfilling.

I've stripped it down today. The fill solenoid operates fine, the drain pump is fine, the main pump runs ok.

None of the internal hoses are blocked, although i did clean a few out.

The pressure chamber was gunked up and the float was stuck. I've cleaned this out, put it back, and tested that the microswitch works as it should.

I took the dosing chamber / matrix out and refitted it. It appears to refill ok when reconnecting the appliance. There is some scuzz buildup in the top left corner, which appears to be part of the drain side of it, not the clean water side. I can't see that this therefore could be the cause of the problem - am I wrong?

What does the machine use to decide it's full? It appears to me that the float in the pressure chamber is for when the machine is OVER full and it kicks the drain pump into action. But what controls the fill volume normally? is it just a timed fill?

Could the fill valve be only partially opening and not allowing sufficient flow?

and thoughts are appreciated. i've never fiddled with a dishwasher before so it's all new to me.

thanks

slip

You need to post the machine E-number (laser engraved on the door lip).

It's SRS45E22GB/01

Fill level is controlled by the upper microswitch on the pressure chamber & switching time is monitored by the pcb. The lower microswitch is the safety level (pump kicks when there is water on the baseplate or when you lift the red arm). Couple of things you could check...is the pressure chamber correctly assembled & does the upper microswitch assy. function properly? Do you have 230v at the inlet valve when it is filling? Are the inline filters clean? Is the inlet hose kinked? A blocked matrix can cause all kinds of strange issues so if it looks blocked anywhere give it a clean. Don't know how old this machine is or if it has an aquastop or a simple inlet valve. But both types can fail electrically or mechanically. A simple way to find out if it works or not is to hotwire it temporarily & check flow.

zipper said:

Fill level is controlled by the upper microswitch on the pressure chamber & switching time is monitored by the pcb. The lower microswitch is the safety level (pump kicks when there is water on the baseplate or when you lift the red arm). Couple of things you could check...is the pressure chamber correctly assembled & does the upper microswitch assy. function properly? Do you have 230v at the inlet valve when it is filling? Are the inline filters clean? Is the inlet hose kinked? A blocked matrix can cause all kinds of strange issues so if it looks blocked anywhere give it a clean. Don't know how old this machine is or if it has an aquastop or a simple inlet valve. But both types can fail electrically or mechanically. A simple way to find out if it works or not is to hotwire it temporarily & check flow.

Click to expand...

Hi there, thanks for your post.
The machine is 5 years old, and has not been any bother until now.

Interestingly, I have (tonight) realised that the top microswitch is a pressure diaphragm operated fill level control.

The machine is partially disassembled right now, and I'll put it back together tomorrow - but - i am pretty sure that when i last tested it, the water level never got high enough in the pressure chamber to activate the top microswitch.

So, tonight, I have wired up the inlet valve and tested it. It does indeed flow, but not very much - maybe 1 litre in about 20 seconds. Any idea what flow rate I ought to see? My plumbing up to the valve is quite high pressure and flow rate, so it's definitely the valve acting as a restriction. Should the valve flow water at a pretty high rate? I wonder if the inlet valve is meant to restrict the flow rate somewhat, hence i'm not 100% sure this is the problem. The installation instructions for the dishwasher say you need a minimum 9L/min supply flow rate. No way is this valve flowing that. Is it faulty?

I've always had a lot of pipe banging as the inlet valve operates. Not sure if that's relevant.

I'm not sure what aquastop is. The inlet valve on mine is just a solenoid and the supply pipe is a plain pipe. My dad's (bosch) dw has a big lump at the tap end of the pipe. Is that aquastop? mine does not have that.

I might replace the inlet valve as a matter of course - but it would be good to hear your views on how much it ought to flow.

A litre in 20 sec is way too slow, my dog can pee quicker than that
As long as your water pressure is good, the isolation valve isn't throttled down, & inline filters are clear (if fitted) then you obviously need to replace the solenoid.
Yes...the grey box on your Dad's machine is an aquastop & it has a dual valve. Yours has a conventional single valve mounted inside the machine. The "water hammer" (banging pipes etc) you have been experiencing can be caused by high water pressure, but in your case a clogged matrix/pressure chamber or faulty inlet valve could well be the root cause of the problem. See how it goes after you have changed the inlet valve & cleaned the matrix.