Bosch SHU43C05UC/37 spray arms not spinning, no rinse action

[topperdude]

Noticed that our Bosch SHU43C05UC/37 is not working as expected. I started a regular wash cycle last night and noticed the timer display 113 minutes (compared to around 99 minutes). So I kept monitoring the dishwasher for about an hour and I got the impression that the rinse cycle was not working. Any time I would expect the machine to be rinsing there would be silence. I thought I heard a faint hum as if a motor was trying to run but nothing else. Specifically, I could not hear the spray arms moving / water sloshing inside the dishwasher either. So after about an hour, I pressed the two buttons to Cancel and Drain. It did successfully drain the dishwasher. I emptied the dishwasher and washed the dishes etc by hand. 

A bit more background - Back in 2013 or 2014, I found out Bosch had a voluntary recall for the SHU43C dishwasher few years back due to a potentially risky issue with the control board. I had checked on Bosch's website and entered my machine's serial number and realized the issue affected machine's manufactured a month or so before the manufacture date of my dishwasher. To be safe, I followed the instructions here to replace the control board with a brand new replacement Bosch control board (purchased from a store recommended by  @Samurai Appliance Repair Man at that time) for my dishwasher model.

Back to current issue - This morning, I dug out and consulted the user manual and per the instructions, removed the upper and lower trays and both spray arms and cleaned them out. Other than some minor mineral deposits from hard water, I did not notice anything else clogging both these arms. I tested further by running water through both the spray arms and confirming that the water was flowing out of the spray arm nossles as expected before re-installing both spray arms. I also cleaned out the Large Object Trap / Cylinder Filter as well as the Fine Filter and inspected any clogs in the drain area while both these were out of the machine. Both these filters also did not have much debris either. 

Once I finished cleaning and putting everything back in the dishwasher, I ran a quick (9 minutes?) "Rinse and Hold" cycle. Here are my observations so far after running this cycle:

1. After pressing the On / Off buttons, I could hear water running for a couple minutes like it normally does. Couple minutes later, the running water stopped. This is when I would expect to hear the rinse action start but again there was silence.
2. I pressed the Off button (did not cancel the cycle yet) and opened the dishwasher door. I noticed there was water at the bottom of the dishwasher. I also noticed steam coming out. I assume the steam is since the dishwasher was from hot water (Just before starting the Rinse and Hold cycle, I had washed some dishes in the sink so I am guessing the water at the hot water inlet of the dishwasher might already be hot and steamy?).
3. I closed the dishwasher door and resumed the cycle and same thing - silence. Waited for another couple minutes and peeked inside again. The spray arms had also not moved from their starting position prior to starting the rinse cycle.
4. In the initial couple minutes after starting the cycles and while I can hear the water gurgling sounds, I can also hear couple clicks (like relays clicking). Not sure what these might indicate (e.g. are these clicks supposed to indicate when the spray arms are supposed to start spining while water is filling up in the dishwasher?) but just thought I'd mention it here in case helps diagnose things at all.

I would appreciate any guidance with further diagnosing the problem (or if I need to check some other things to help diagnose the issue).

Thanks much in advance,
-Topper

[Vance R]

From your description of slight hum sound with no sound of water spraying it would seem the wash pump is not running. Could be jammed or seized causing your issue.

[topperdude]

21 hours ago, Vance R said:

From your description of slight hum sound with no sound of water spraying it would seem the wash pump is not running. Could be jammed or seized causing your issue.

Thanks so much for your response - it is guiding us in the right direction to better understand the root cause of the issue. 

Based on your feedback, I searched on youtube and came across this video which talks about identical symptoms in a Bosch dishwasher that looks pretty much the same as ours and also shows how to check and remove any objects (broken glass etc.) that may be stuck in the impeller and preventing the impeller from running and cause it just hum: https://www.youtube.com/watch?v=q_l3dDwU2X4

I followed those steps and felt inside that drain area but could not feel any objects like glass etc. I also took a picture down that drain and can see the (green) impeller but am not sure what the round thing above the green impeller might be and if it might be normal for that white (round-ish) thing above the impeller to be there or could it be what might be causing the impeller to "jam"? I have attached the picture to this post.

Any idea what that thing above the impeller could be? And is it normal for it to be in that drain above the impeller. We are wondering if that white thing above the impeller might be part of a mechanism to prevent debris (like broken glass etc.) from getting into the pipes and spray arms and somehow it might be stuck in that position and preventing the impeller from normal operation? And if so whether there might be a way to "reset" it?

 

Would appreciate any input.

Thank you again,

-Topper

 

[Vance R]

9 minutes ago, topperdude said:

Any idea what that thing above the impeller could be?

If your referring to the black piece it is probably the coupling rubber from the sump to pump. Here is a picture from the parts explode view to show the couple, item #0423. 

Watched the youtube video, that guy got off easy. If you don't see or feel anything it would be time to remove the pump to inspect inside.

[topperdude]

I have been having a hard time finding the replacement impeller kit for this dishwasher. Are there other marketing / parts sellers that might have the impeller kit OR Is the only option to replace the entire circulation pump? (I would prefer not going with used / ebay / non-authorized sellers).

Thanks for any input,

-Topper

P.S. We have been just manually washing the dishes by hand since the dishwasher stopped working in Feb but today a friend (more handy than me) is planning to stop by to help remove the dishwasher and take it apart per online instructions to diagnose whether it is just cleaning impeller OR replacing damaged impeller OR replacing entire circulation pump.

[Nathaniel Peterson]

On 5/30/2023 at 4:21 PM, topperdude said:

I have been having a hard time finding the replacement impeller kit for this dishwasher. Are there other marketing / parts sellers that might have the impeller kit OR Is the only option to replace the entire circulation pump? (I would prefer not going with used / ebay / non-authorized sellers).

Thanks for any input,

-Topper

P.S. We have been just manually washing the dishes by hand since the dishwasher stopped working in Feb but today a friend (more handy than me) is planning to stop by to help remove the dishwasher and take it apart per online instructions to diagnose whether it is just cleaning impeller OR replacing damaged impeller OR replacing entire circulation pump.

Don't get the ebay pump my boss got two that didn't work or was damaged in shipping.