Question about Bosch 23 in. SHU 8805 Built-in Dishwasher

2 Answers

Bosch Dishwasher Hums But Doesn't Start

After making more noise than usual our Bosch dishwasher SHU8805uc/14 no longer works. When we select a cycle, press the start button and close the door, the unit only faintly hums: no water enters the unit and it sounds like no moving parts are working. There is no water in the pan below. If I press and hold scrub and regular buttons and press start and close the door, sometimes water begins filling the unit for a couple of seconds and then it stops and just hums. Once when doing this it sounded as if the motor began to run for a few seconds and then stopped, again only a faint hum. If I do it again, sometimes the unit will drain the water from the previous test, but will not run. I pulled the unit out, took off the left panel to expose 2 micro switches. If the unit is set to cycle and turned on I can get it to fill up with water by activating the switch attached to a white translucent vessel. If I then activate the red float switch the unit drains. I observed no leaks.

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  • 2 more comments 
  • craig821 Jun 18, 2009

    Thanks for the reply, but "If the unit is set to cycle and turned on I can get it to fill up with water by activating the switch attached to a white translucent vessel." Doesn't this mean that the water inlet is not blocked and that the solenoid is working?

  • craig821 Jun 19, 2009

    Thanks for your help! I am now getting a clearer understanding of where the problem lies!



    The image you show here is indeed what I was refering to as one of it's parts being a white translucent vessel (I was referring to the white translucent disc with the blue piece of plastic which resembles the shape of a question mark), except that your image is rotated 90 degrees counterclockwise from the actual condition.



    Because I was troubleshooting before with a malfunctioning unit, it is now apparent that I wasn't starting a cycle from the beginning. Ok, If I start with dry unit and engage a new wash cycle water indeed enters the unit and fills until the blue piece of plastic turns the water off. So far so good.



    Now the faint hum begins. There is no sound of "washing". Having worked with small electric motors before, this hum sounds like a motor that is not spinning, just humming. It hums for about 20 seconds and then stops for about 15 seconds, then it hums again and then stops, and so on. I assume that the stopping is a safety tripping and then resetting.



    If you agree so far, is the problem the motor or what it is trying to operate (a pump?) and are either of these likely to go bad? Please recall in my first post that the unit began to make alot of noise as soon as the washing started, thereafter it stopped working.

  • craig821 Jun 19, 2009

    I thought that we were narrowing the problem down to the motor and the pump...I agree that the controller could be the problem. But if it is the controller, then that leaves a couple of questions!



    What impact do you think the controller has had on the screaching noise during the motor operation before the unit failed?



    If the controller has failed, what is humming sound now after the unit is filled with water?

  • craig821 Jun 20, 2009

    How do you access the impeller & motor? From the left side, right side, back, front, bottom, or from inside the washing chamber? Do you have a picture or diagram that you can share?

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  • Bosch Master
  • 19,396 Answers

If this happens at start of the cycle, then it is likely a problem with the water inlet system.

First thing to do is accessing the back of the machine, with power unplugged.

Check the water supply hose, and ensure that water is flowing inside the machine. If the inlet hose is OK, then the problem is likely the inlet valve.

Access the inlet valve and remove hose from valve. Check if hose or valve is blocked. If there is no blockage , then the valve is probably faulty.

the valve can be tested first reading ohms at the solenoid contact with a multimeter, and energizing the valve to see if it close and open. Also reading valve volts can tell you if problem depends on valve or timer control board.
The last two test involve reading values and operating valve with live power. For safety reasons they must be done by an experienced repairer.

You can find parts and diagrams for many appliances here.

If this comment had been helpful, then please do not forget to accept the solution.

Many thanks.

G.

Posted on Jun 18, 2009

  • Ginko
    Ginko Jun 18, 2009

    If the inlet valve is opening under certain conditions then the valve is fine.

    The translucent vessel you are talking about must be tha water level switch.

    Under normal conditions the water level switch closes the inlet valve and opens the drain pump when an overflow is detected.

    In your case it looks like the water level sensor is defective, and is closing the inlet valve from start, wrongfully detecting overflow even when there is no water.

    The humming noise can be the drain pump operating with no water inside the machine.

    Here is the water level switch:



    Regards.

    G.




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  • Master
  • 6,784 Answers

Hi.this seems like a multi-dimensional issue but, its just a control fault. the control unit has failed. the logic chip set is damaged. these chips are responsible for initiating the correct wash sequence. this control unit should be replaced in order to restore normal function to your unit.

Posted on Jun 19, 2009

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  • Michael Masters
    Michael Masters Jun 19, 2009

    The Control Unit will cost about $105.00

  • Michael Masters
    Michael Masters Jun 19, 2009

    This humming and screeching can be caused by an foreign object that has successfully traveled and made it passed the chopper or filter, into the wash or drain impeller. this will jam the impeller temporally. you can remove the sump or pump housing to check for this type of interference if you choose to but, this is totally unrelated to the original issue. you may have two issue here but, the main is the control unit. the actual control can cause a slight hum if the circuits are damaged.

    It controls the initial actions of every electrical parts that are housed in the unit. it is responsible for switching the valve and motors as well. if this unit is faulty, it will cause the hum in the motor, due to a failed relay circuit.

    I suggest you inspect the circulation motor. remove the housing and, look to see if the motor is jammed. try to move the drive with your finger. if it moves freely, it may just be a foreign object that was caught in the housing. I doubt this but, the inspection will rule it out.

    I recommend inspecting the drain pump as well. most units will have a motor set up that will incorporates a single motor that will have to impellers attached. one is the wash and, one is the drain. if this is the case, the test will be simple.


    FYI, The previous expert didn't respond to your last post so, the issue was forwarded to my board. i assume the previous expert was a bit overwhelmed. i do not have access to your previous encounter with the other expert. You stated we were chatting about other issues and not the control. this must be a mistake. that chat was with the previous expert that didn't finish this chat.




  • Michael Masters
    Michael Masters Jun 19, 2009

    Concerning the Motor. If this jam is significant, the control will prevent further damage by throwing a protect switch. this will kill the entire unit. during the inspection, if you detect any impeller damage, replace the failed impeller and drive as well. if its very severe, as soon as you remove the housing, the impeller may fall out. In most cases, small pieces of glass will get jammed and, this will cause the motor to strip the center stud. this will cause loud noises and trip the protect mode as well.

  • Michael Masters
    Michael Masters Jun 20, 2009

    Your main concern will be the circulation motor. this is what you want to inspect. its housed in the pump housing on the bottom on the unit.there is a picture of the pump with the upper case attached below.


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I have a Bosch SHU9955US/14 (Integra) dishwasher. There is currently a 0 with and asterisk showing on the display and the unit will not run.


see this causes and fix it. God bless you
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