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Bosch Dishwasher SHU5305UC/U12 low/no circulation pump pressure

6 posts in this topic

My Bosch Dishwasher SHU5305UC/U12 suddenly has no wash pressure from the circulation pump.  Just a trickle from the lower arms, with arms removed maybe 1-2" of head from the outlet tube on the floor of the dishwasher.

 

I was hoping to preemptively order some parts for this before doing the major exploritory dismantle, but I am a little stumped as to what is causing this based on the circumstantial evidence I have. Stuff I know so far:

 

• very little pressure/flow from the circulation system.

• Reached into circulation pump inlet and found no blockages

• put a socket on the circulation impeller and it turns freely.

• Circulation pump motor reads 10.8 ohms at the control board.

• Circulation pump motor is drawing 1-1.1 amps.

• water heater had been working in the past, not coming on now, but I assume that is from the circulation flow switch not activating do to low flow?

• Circulation pum seems to run fine under power, but the noise it makes is different from before.  I can't tell if this is pump cavitation do to a blockage, or something else.  The motor does turn freely with a socket and I couldn't feel any dragging, scraping, bad bearings etc.

 

 

My guesses at this point without dismantaling and actualy looking at the thing are: 

 

Missing/broken impeller vanes?

Some kind of blockage between the pump and the outlet.  Is it possible to have a blockage there, it seems like it is just the heater module and pretty wide open space.

 

thoughts?

 

Thanks!!

 

 

 

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Need appliance parts? Call 877-803-7957 now!

While turning the impeller from inside tub have someone else watch the fan blades on the motor with a mirror under the machine.

 

Most likely you will find when turning the impeller the motor isn't actually turning, thus when motor is running, impeller isn't turning or is only turning very slowly from friction with back portion of impeller which front vane section has broken away from.

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Adding a little to this, make sure when turning the impeller from inside the tub area not to push inward with too much pressure while turning because this will shove the two impeller halves back together and possible make the actual motor turn and make you think the impeller is OK when in-fact it is the problem.

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Impeller replacement went well.  The impeller vanes had separated from the plate that threads onto the motor shaft.  That why I was feeling a good connection from the impeller to the motor.  It just wasn't connected to the vanes.

 

Now for new problem.  After a test cycle the dishwasher just keeps filling, even when it is off.  I would immediately suspect the fill solenoid.  But wow thats a coincidence that that would go out within one wash cycle of changing the impeller.  I took it out, tests at 1000 Ω can't blow through it, tested the two micro switches on the left hand fill assembly manifold thingy both test good on both poles.  all the linkages seem clear and functioning to the micro switches.  Blew on the diaphragm actuator that engages and disengages the micro switch fine.  Anything I missed before changing the solenoid?  

 

TIA!

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