Dishwasher stopped washing but still drains. I took apart and found that where metal piece in chopper and screen completely clogged. Where the chopper and impeller meet each end is broke. How do I know if the motor is still good therefore only replace chopper and impeller.
Here are your parts
Replacement parts for WHIRLPOOL GU1200XTLT0 Undercounter Dishwasher | AppliancePartsPros.com
Often if you click on a parts picture a new page will open with more views of that part. Then clicking on a new view should expand it so you can see it better.
Here is the tech sheet
http://www.servicematters.com/docs/wiring/Tech%20Sheet%20-%208533399.pdf
Manually rotate the motor’s armature to ensure the bearings etc. are OK.
Check the windings with a meter to see if they are OK
If both OK then motor is probably good
OR
Remove the motor from the unit and hook it up to a line cord and give it a try. You may not even have to remove it from the machine.