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netpog  
#1 Posted : Friday, June 24, 2016 7:10:52 AM(UTC)
netpog

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[UPDATE: I fixed the problem. See my reply, below, for details and suggestions.
NEWER UPDATE: Nope, not fixed. I've stronger spray, but I still have residual soap. See my latest post, please.


After years of reliable service, this 2012 dishwasher now USUALLY leaves some undissolved soap in the dispenser. (No change in the detergent used. No improvement when using brand-new detergent. Nothing blocking the lower rack. Water pressure is high. Dispenser does open.)
I have whipped open the door mid-cycle, and seen the lower spray arm rotate another few inches, but I cannot tell whether the upper spray arm is rotating at all. It seems to change position between peeks, but might be rotating slowly or intermittently. The arms are pristine inside. The sump area, including the impeller, is clear.
MY QUESTIONS:
(1) Might a stiffly-rotating upper arm be the problem? (It spins when poked, but not incredibly smoothly.) Shall I replace it, just to see? It's cheap enough.
(2) How can I tell whether the impeller is disengaged from its shaft, or if the pump is enfeebled? I can't find any service manuals for the "SHE" series.
(3) What other causes should I consider? Might there be a control-board problem? (I gather those happen, often from easily-fixed bad solder joints.)
NOTE: The hot water is, and was, via a tankless that hates low-flow appliances, shutting off below 0.5 gps, so the D/W has always needed to do its own heating. Using a clamp-on ammeter, I have confirmed that the DW's heater is functioning, at least when I'm looking.
THANKS MUCH for all the expertise this forum provides, and sorry for the long query.
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kbedard  
#2 Posted : Monday, August 1, 2016 5:49:25 PM(UTC)
kbedard

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I've had the same issue. My Bosch is only 6 months old. I took off the soap dispenser cover and cleaned it, as some poster suggested. But honestly I had little hope for that. Then I spun the upper arm, under the top tray, and it was very sluggish. I was able to easily take it off and clean all pieces. Now it rotates nicely. I am very confident this will take care of the soap issue. It is running now, so we'll see.
netpog  
#3 Posted : Thursday, August 11, 2016 11:26:40 AM(UTC)
netpog

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Yes, for residual-soap problems, a clogged or blocked upper arm is the usual problem. But in my case, I got immediate relief when I replaced the circulation pump. That pump includes the heater, so it's often called the "heater pump". The part number was easily accessed via the parts diagrams at Bosch Home Appliances And you can find a Bosch 800 series dishwasher service manual online, which is very helpful.

NOTE TO ANYONE WHO DOES THIS WORK: Contrary to the service manual, you don't need to do a ton of disassembly, and fold down the tank, to get at this pump. I just put the unit up on bricks, to get a few extra inches, and could easily-enough remove/replace the pump from the back of the unit. But the service manual was otherwise helpful. It includes instructions to diagnose the pump (measuring the resistance), but be warned that my old pump wasn't doing the job, despite the fact that it metered out just fine. Perhaps the impeller, inside the pump, was damaged. But Bosch says that for these heater pumps you shouldn't disassemble the pump; you should only replace it. (The impeller inside the heat/circulation pump is different from the drain-pump impeller, which you can easily access from the sump, inside the dishwasher.)

Also, the instructions for running the test program, and for accessing the error codes, were impossible to find online, and AppliancePartsPros could not help. Turns out there was a single big sheet of paper under the dishwasher, with all that information, as well as wiring diagrams.

Now I know, and I hope somebody else finds this useful.

My dishwasher is working MUCH better. I did get some soap residue, but only once, and probably due to my blocking too much spray with unusual items. I'm going to replace my upper arm all the same, because mine rotates a little stiffly, and the new assembly is very reasonably priced.
netpog  
#4 Posted : Monday, September 26, 2016 11:05:41 AM(UTC)
netpog

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Replacing the pump & spray arm increased the strength of my water circulation. Now, when I open the door mid-cycle, I'm likely to get my face sprayed, which never happened. But now I have what I suspect are two problems:

1) Sometimes ALL the soap is remaining.
I suspect that the dispenser intermittently fails to open during the wash. It then opens during the rinse cycle, because the same signal actuates the dispenser door and the rinse aid. So I'll look for a bad solder joint or connection.

2) USUALLY there is SOME soap remaining.
I'd love to confirm that the dispenser door opens when it should, so I'd love to see the timing chart for my model. (I can only find it for older units.)
I suspect that this is the fault of my tankless water heater, which can't seem to detect the water flow to the dishwasher. (Dishwasher draws 0.67 gpm, and the tankless display shows 0.0 gpm while it does so!)

Even though the dishwasher has a heater, that heater only runs during the middle of the wash & rinse cycles (if the old SHU-series timing chart is to be trusted). So would the cold water cause my soap-residue problem?

THANKS!
Nickmey  
#5 Posted : Monday, October 3, 2016 3:21:20 PM(UTC)
Nickmey

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Hi, as for the opening of the dispenser door, it always happens at the same time in the main programme, just after the water has attained working temperature. A relatively loud "pop" can be heard from the front of the machine.
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