Author Topic: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle  (Read 5309 times)

Offline qman

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This dishwasher has been absolutely fabulous all the years we've had it but recently it just hasn't been doing the job.  Intermittently, the dishes look clean when the washer finishes but they have a gritty feel to them.  When this happens there is usually some grungy looking water in the bottom and sometimes there is quite a bit of water in the bottom.  So yesteray I ran a complete cycle and paid attention to it all the way through.

I believe the dishwasher usually has 3 stages to a single clean cycle. I believe the first stage is a water only pre-wash. The second stage is the soap wash (usually the longest stage) and third is the rinse. Today I paid attention to a complete cycle and it seemed that the unit used the same water all the way through. During the initial stage the water is usually the dirtiest. With this particular load, the water in the initial rinse stage had a pinkish strawberry milkshake look to it. Shortly after the second soap stage began, I opened the unit and noticed that water looked the same as it did during the initial stage. It had the same pinkish milk shake look. I was sitting on the floor when the soap stage finished. It began to drain but didnít completely drain all the dirty water. It only drained for a few seconds (probably less than 15 seconds) and than began what I believe was the 3rd stage, the rinse, using the same dirty pinkish milk shake water. While it was draining after the second stage, I could feel hot water in the drain hose and in the sink drain pipe so I do not believe there is a clog anywhere in the line. It just didnít drain for very long. What would make the unit act like this? I like conserving water but not like this.

BTW, the water level was up around the top of the microfilter screen that screws into the bottom of the unit. This looks correct but I threw it in here just in case it isn't right.

Again, this problem is intermittent but happening more and more often.

Also, I read this thread:  http://appliancejunk.com/forums/index.php?topic=2583.0
I don't seem to have and underfilling problem.  It just seems like this dishwasher forgot that it should change out the water between stages of a wash cycle.

Offline qman

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Re: Bosch SHU9925 Dishwasher Using Same Water through entire cycle
« Reply #1 on: December 27, 2008, 06:05:26 AM »
Sorry, I titled this thread incorrectly.  It should say "Dishwasher Using Same Water"

Offline JWWebster

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #2 on: December 27, 2008, 09:46:43 AM »
Remove the pump filter and clean out the sump If you have something in the impeller it must be cleaned and objects removed. Kill the power and pull the unit. Get out the assembly and clean it. I have your dishwashers service manual in my computer but I do not know how to post it. Perhaps AJ can help.
« Last Edit: December 27, 2008, 09:50:24 AM by JWWebster »
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Offline qman

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Offline Repair-man

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #4 on: December 27, 2008, 11:32:34 AM »
Yes, it will cover the basics. There  is another Bosch post that shows the water distribution on the left side of the unit:

http://appliancejunk.com/forums/index.php?topic=2583.0
« Last Edit: December 27, 2008, 11:34:34 AM by Repair-man »
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Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #5 on: December 27, 2008, 12:23:38 PM »
What do you mean get out the assembly?  Do you mean the impeller assembly?

Offline JWWebster

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #6 on: December 27, 2008, 01:01:49 PM »
Yeah that is the manual it says 9925 on the 1st page. On page 15 0f 37 in this manual it says do not remove the pump, get the screen off the sump and reach through it to the impeller and get the crapola out of it. Well it didn't say crapola but you get the jest.
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About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
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Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #7 on: December 27, 2008, 01:08:31 PM »
Alright, I pulled the drain impeler out and it is clean.  It also turns just fine  All hoses and water flow parts are also clean.  There is no blockage.  The impeller is on the left side of the sump and there is some kind of motor on the right. I'm guessing this motor is the water flow motor for getting water up into the unit.  I only looked at the impeller, not the motor.  It looks like removing the motor is a real big job.

Is it possible that the controller has lost it?  I say this because sometimes it works perfectly fine and other times it doesn't.  It started to drain and then stopped.  To me its acting like its brain is fried.  Kinda like I would after a 2x4 upside the head.  Just wondering.

Another thing.  When I removed the door, the inner door is coated in some thick, heavy, black tar-like gunk (I guess soundproofing).  Anyway, the black/white wire (ground?) to the controller looked like it had melted into the black tar stuff.  There were a number of wires in the harness there but only the black one was into the black stuff.  Does that mean anything?

Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #8 on: December 27, 2008, 02:49:43 PM »
I pulled the dishwasher out, removed the left panel and ran it.  This is water level control unit in my washer:

http://www.repairclinic.com/SSPartDetail.aspx?s=t-shu9925uc-%3d%3di935595&PartID=935595

In the picture the unit is upside down from how it is mounted.  If you'll notice, in the center is a cylindrical chamber that unit has a red thing in it.  I believe the red thing is a float of some type.  Hanging over the edge of this chamber is a candy-cane-shaped piece of plastic (about as round as a straw) that hangs over the side.  Kinda how a candy cane would if you hooked it onto a glass.  I think the way it is supposed to work is the chamber fills with water and the red float rises.  If it rises high enough, it pushes up on a candy cane shaped plastic that depresses the drain impeller motor.  I can lift the candy-cane-shaped thing by hand and it pumps out fast.  But as I sat there and watched it, it only pumped for 4-5 seconds real fast and then slowed way down for a few seconds and then quit.  Then the second wash stage began.  Anyone have any ideas?

Here's how I observed the washer working.  It begins by allowing water in.  Once enough water enters the unit it begins to run.  I can hear the wash arms spinning and spraying.  Water continues to flow into the unit until the proper level is reached.  I was watching the red float and noticed that it started to rise at the beginning and when the unit started to spray water, the water level in the float dropped because there is now water being circulate up into the washer which makes for a lower level in the bottom.  I think what is supposed to happen is that when it is time to change wash stages, the unit stops circulating water, the water level then rises, pushing the float up into the candy-cane-shaped thingy which then engages the drain impeller switch.  This is only happening for a short period of time and never emptying the unit.  It then starts up on the next stage with the same water that it ended with.

Offline JWWebster

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #9 on: December 27, 2008, 03:26:30 PM »
Can you see why it is important to clean out the sump?
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About the icons: The beer is tip link, if a tech saves ya some money buy em a 6 pack. The small green square=personal message. The green dot is a link to my web page on appliance repair and other general BS I love to post. The letter sends me email.
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Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #10 on: December 27, 2008, 04:09:07 PM »
I have an update.  And BTW, like I said earlier, I always keep the sump clean.  And in this case, the sump was spotless and the impeller is fine.  I'm not trying to be a jerk.  Its just that this is the third forum I've gotten on looking for help and every time I keep hearing "clean out the sump" as if that is all anyone knows about.  I'm not trying to put you down as I see you have a pretty good reputation.  But lets get past the sump.

Here's what I've come to learn.

I tore apart the water distribution system.  On top of that distribution system is the water inlet switch.  It is a pressure operated diaphram.  As the water level rises air is pushed up into the thing and a diaphram pushes out on an actuating rod that clicks a switch.  The first time the switch clicks the washer starts running and the water level drops.  It continues to allow water into the tub and the second time it clicks water flow into the unit is stopped.

The red thing I spoke about earlier does not control the drain pump.  It is an overflow device. After the washer was running I took and poured a gallon or so of water into it which made the float rise and start the pump.  Once the float dropped to the proper level the drain pump stopped.

I then sat there and watched the stupid thing.  Great way to spend a Saturday eh?  When the pre-wash stage ended the pump kicked on and drained like a banshee.  It drained for a good 30 seconds like the book says it should.  When that finished I opened the door and it was empty.  After closing the door it started filling once more with clean water.

So I'm stumped.  This time all worked well.  Last time it didn't.  This is what I mean by intermittent.  I didn't fix or clean anything.  All I did was
  • disconnect the plugs to the fill switch and overflow draim pump switch
  • take apart the input control thingy (to understand what it did)
  • put it all back together and run it again
That's it.  So what controls the pump at the end of the three stages?  Whatever does that is the culprit.  Either that or the impeller sometimes just can't pump.  But I don't think its the impeller.  It spun just fine and the problem is that it can't pump, its that it doesn't pump for very long.

Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #11 on: December 27, 2008, 04:18:53 PM »
Sorry about that first paragraph on my last post.  It reads like I am being a jerk.  I meant no offense.  But the one thing I have always checked first has been the sump.  We have had this unit for about 5 years and in the past everytime the dishes had that grainy feel to them it was because there was a small item stuck down in one of the sump tines.  Some of the things I've found in there were a kernel of corn, a pea, a small piece of sausage, some sunflower seeds.  Every time I'd remove it and re-run it and all would be good.  So when it comes to the sulmp, I've become a sort of expert at cleaning it out.  My wife has been complaining about this thing for a couple months now and the difference has been that many times I haven't found anything in the sump which is why I'm wasting my Saturday laying on the kitchen floor staring at the bowels of our dishwasher.  Not that I'm complaining, I kinda like how this thing is designed and its pretty cool to learn how these things work.

And JW, I appreciate you using some of your Saturday to pitch in and help.  I have another question though.  Do you have any idea why the micro-filter on these units allows things like corn kernels and the like to get down through it?  The down tube of the filter has two baffles in it that will let things fall through.  It just seems counter intuitive to me that a filter actually has a way through it.

Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #12 on: December 29, 2008, 11:04:21 PM »
Update:  Ran it twice today using the rinse only cycle.  It did not drain either time.  I scooped out all the water, removed the sump cover and there wasn't anything I could see in there .  The impeller moves fine.  So I stuck my finger into the drain hole and felt something.  I used a hook shaped wire to grab it and lo and behold I start pulling out some sort of round rubber thingy about the size of the drain hole.  I was about to yank it out until I realized that it just so happened to be the size of the hole.  Is this thing supposed to be there?  It is attached and I'd have to rip it out.  The only thing I figure it could be is a type of check valve so that water doesn't come back in to the unit.  The schematic I have doesn't show it.

Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #13 on: December 29, 2008, 11:07:25 PM »
Never mind. This is it:  http://www.appliancepartspros.com/partsearch/model.aspx?model_id=232307

In my dishwasher it is black.  this one is clear.  What is it?

Offline qman

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Re: Bosch SHU9925 Dishwasher Not Using Same Water through entire cycle
« Reply #14 on: December 30, 2008, 02:43:46 PM »
Another Update:

It took me a while but I finally figured out the schematic.  The drain pump is operated by 2 things.  One is the overfill switch (which works fine) and the other is the control unit.  It pumps just fine anytime I engage the overfill switch.  It does not always work fine when it is suposed to empty the unit after a clean stage.  Does this mean the controller is shot, or maybe somewhere wires connect between the controller and the pump?

 

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