Dishwasher fills and drains but won't run

Dishwasher Repair
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So brief backstory: I had a partially clogged kitchen drain, which took a significant amount of snaking/plunging/boiling water to clear. But it is now cleared and draining quickly. The slow drain was discovered because my dishwasher stopped working. Just running the faucet did not produce enough water volume to back up the drain, but when the dishwasher pumped out its water it backed up into the sink.

My dishwasher (Whirlpool WDF520PADM3) still won’t run. Behavior is: it fills up with water, it drains (presumably to test the drain speed?), then it fills again, then it just sits there.

From the diagnostic mode, it reports the following error codes: 6-4 (float valve open) and 8-1 (drain too slow). However, the float valve moves freely and appears to be working (when I pull it up manually, I can hear the relay switch click), and when the dishwasher drains (e.g., if I fill it and then manually enter drain mode), it drains freely without backing up.

I have tried "resetting" the dishwasher (it is hard-wired, so I turned it off at the breaker for a few minutes and then turned it back on), to no avail. If I start it up, the behavior is the same.

At my wits end here. Any help or additional troubleshooting steps would be greatly appreciated. It’s almost like it’s stuck in some error mode from when the drain was clogged and I can’t get it to reset.

Thanks!

  • Quick update … so I "reset" it again, and when I start it up (in 1-hour wash mode because the damn thing takes like 4 hours to run through a normal cycle), it fills and then makes a noise that I would describe as bullfrog-esque (the pattern is duh duhduh). I can hear the clicks that I assume are the dishwasher attempting to switch cycles and then it just makes that bullfrog noise repeatedly. I turned it on, let it be, and come back 2 hours later and it’s just sitting there full of steaming hot water baking food onto my dishes for the 13th time.
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The clicks might be the diverter motor positioning the water flow.

If there is no washing action while the unit is full of water, it might be because of a bad wash motor.

If you have long enough electrical wire and water supply hose to advande the dishwasher out of under the counter, you can start a cycle and check if you have 120V to the wash motor under the dishwasher.

If 120V AC goes there but the dishwasher doesn’t wash and draw 0 Amps from the start, it’s likely a bad motor. If there is a current detected when starting the cycle, but it drops to zero after a few seconds/minutes, there might be something blocking the impeller, and the motor protection system turns it off before it overheats.

Please note that most Whirlpool wash motors have a small PCB inside the motor, so it’s not as simple as reading windings resistance.