Hi, I have a Whirlpool Quiet Partner I that is NOT SO QUIET!!! 
It has started making a LOUD howling noise during the wash cycle.
The model is DUC600XTPQ7 and serial is FTO402066.
Can you tell me a)what you think is the issue and b) how to go about fixing it (where to find the parts diagrams, where to buy, etc.)
I would really appreciate it. I previously posted a year or so ago about our oven and you really helped a ton!
Thanks!!!
Remove the upper dish rack.
Remove the water feeding tube for the upper spray arm.
Remove 4 screws (#3 on the break down diagram) holding the top cover (#1).
Remove the inlet protector (#8) holding by the tab on the right side.
Check the chopper (#6) for any clog.
Check for any foreign objects in the pump sump.
Clean all debris and assemble in the reverse order.
If it would not help, then the problem most likely is a bad motor.
Here are the breakdown diagrams and Replacement parts for WHIRLPOOL DUC600XTPQ7 UNDERCOUNTER DISHWASHER | AppliancePartsPros.com
Gene.
I have the same problem, and cleaning out the sump etc did not help. Would you recommend replacing just the motor (AP4434021), or the entire motor/pump/sump assembly (AP4434612)?
On a related note, sump housing AP3866228 has a 32.17mm hole for the thermistor and says if my thermistor is 31-31.5mm I should order sump housing AP3775547 instead. 0.67mm is a very, very small difference; I don’t think I could measure it that accurately. But then in the complete sump and motor assembly AP4434612, it says that sump has “the larger 23.96mm hole for the thermistor” - described as being larger, but it is smaller than the hole size listed in both of the sumps sold separately. There’s only one thermistor listed, with no size given. Now I really don’t know what to order. Please help!
What is the complete model number of the dishwasher?
What exactly is the problem?
Gene.
My apologies, I didn’t realize there were multiple models of “Quiet Partner I”. Mine is model DU1055XTSQ3, serial FW1206371.
It makes a loud sort of howling noise during the wash cycles, much louder than when it was new a few years ago, and louder than even a month or two ago. I cleaned out some debris from the chopper area, but the noise did not change; I disassembled it again just to make sure, and there was nothing else in there.
A noisy motor bearing has been one of the most common issues with those dishwashers. You can try to repair the motor as it was discussed in one of our previous threads: http://forum.appliancepartspros.com/dishwasher-repair/22693-whirlpool-gold-quiet-partner-iii-noisy.html or just replace the motor.
I would suggest the whole new pump & motor assembly replacement as more reliable repair than just the new motor, but there is $40 difference for parts.
Here are the breakdown diagrams and Replacement parts for WHIRLPOOL DU1055XTSQ3 UNDERCOUNTER DISHWASHER | AppliancePartsPros.com
Gene.
Thank you. Replacing the bearing for $1.77 is tempting, but it’s such a pain in the (neck) to uninstall/reinstall in my particular installation, rather than risk having to pull it out yet again to replace the motor if the bearing fix doesn’t work, I think I’ll just sink the $150 and replace the entire assembly, once and done. I’ll place my order shortly. Thanks again.
You are welcome. Keep us posted.
Gene.
I replaced the complete pump / sump assembly. Really the only hard part was getting the sump seated in the bottom of the tub; I laid the machine over on its side and from inside the tub, pressed the whole sump assembly firmly into the hole, and my wife installed the three wedge / clip / retainer things from the other side.
I disassembled the old motor: the bearing on the impeller / volute end was almost completely frozen.
It is now MUCH quieter; the noise of the water splashing around inside is actually louder than the motor.
Very satisfied; thanks very much!
You are welcome. I’m glad it’s up and running.
Gene.