My Whirlpool WDT720PADM dishwasher stopped functioning properly last night. It will run through a full cycle, filling, draining, heating, soap door opens and steam vent opens at the end. While running, the main pump never sprays water or makes noise. I hear a relay click when it should come on, but it does not. It does not hum, just does nothing. I ran the diagnostic check on the machine and no new fault codes have been recorded. The dishwasher's processor thinks all is good. I also left the breaker off all night thinking perhaps something would reset by the morning. No good.
So, I opened the cover and tested the main motor's fuse through some pins on the board, it had proper continuity and negligible resistance. I tested resistance through the main motor through the two large blue wires running to it and it registered between 11 and 12 Ohms. I also found no continuity from either motor lead to ground. Finally I gave the motor 120 volts AC through the two large blue leads, flipped to try both polarities and got no movement or noise.
I am not able to test directly against the motor so there could be other smaller wires going into it that I do not know about that could have an impact. I also tested resistance on an old, known working, dishwasher pump motor and got around 11 Ohms, so I figure that number was reliable. I was almost ready to call it a day and order a new motor assembly, but ran one other test with the dishwasher running and at a cycle where the motor should have been running. There was no voltage across the two blue wires that run to the motor and I expected there to be. Now I am confused.
Are there better ways of isolating the problem without taking the pump out of the machine? That is the next step I think, but I would like to avoid it if possible.
In the image below, two green lines point at the two blue wires I have been testing the motor with. One looks red; it is blue with a red stripe. Other is blue with a white stripe. They are next to the hot and neutral lines from the wall.