I ran it through a cycle the other night and after opening the door, found the dishes were still dirty and the detergent tablet was on the floor of the tub, half dissolved. I removed the access panel and started the dishwasher to observe what was happening.
The dishwasher begins to fill with water as it normally would (I can hear the fill valve opening, water running into the tub, and beginning to slosh around in there). However, instead of filling for 30-40 seconds and continuing with the wash cycle as it normally would, after about 10 seconds of filling I hear (and see) what appears to be the drain valve open, and the water drains from the dishwasher into the disposal. This cycle seems to repeat itself, so the tub is never filling up with water to wash the dishes with.
The various troubleshooting steps I've found online say what would cause the dishwasher not to fill, or not to drain, but it appears mine is doing each of these - just a little too soon after one another. I checked the float and the drain trap, and nothing appears to be interfering with either. No kinks in either the drain or the supply line, either.
I have attached a picture of the valve I can hear and see moving when the dishwasher begins to drain (to the left of the motor); I believe this is the drain valve/solenoid?
Why is it opening so soon after filling begins? Any idea what the trouble could be?