Hi,
I have an older dishwasher also and recently mywife also complained about it not cleaning right... so me being the man I amtried in vain to clean the things... Bought new spray arms online and installedthem in minutes...now the thing works like new... However I have also foundthat if the heating element goes bad then that also can mess things up bad...So I would buy new spray arms, and also check out the heating element to makesure it is working... Here is a tip that will help you with the onlinebuying...
Dishwasher SprayArms not Spinning
using tape measure measure your item of here is dimensions. you can buy a DW that is 24 inches wide, very easy to do. It is a standard size DW
Width23.875"Depth24.5"Height33.875"
Try a mainboard Reset. Pull the mains plug before bed tonight. Tomorrow, press and hold the on button for 30 seconds, then let go and plug it back in.
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My plan was to see if I could find you a service manual, but strangely, the only reference to that model number is your post here! My guess is the D6 is 'D for Dishwasher' and 'Series 6' or 6 models in that current series.
If the machine has been laid up or little used, check all the connection on the control board. Clean pins and plugs with electrical switch cleaner
https://www.google.com/search?q=DU940QWD6
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Most likely a bad heating element..
https://www.youtube.com/watch?v=am-fhX92rbw
You can call Repairclinic 800# too, and talk with a tech, before throwing parts at it. 800-269-2609.
Best to you.
Miniplayer (i)
We'll also want to shut off the inlet watersupply and disconnect that as well.
0:30/8:42
Please refer to youtube " Whirlpool Dishwasher Repair - How to Replace the Pump (Whirlpool # W11032770) "