Whirlpool dishwasher, about 15 years old. It has had increasing trouble in draining, though it usually (with the exception of one time) works when you push “cancel drain”.
The first thing you think about is clogs, so I took out the filter etc. the other day and cleaned a bunch of debris out (several shards of glass, toothpicks, a twist tie or two, and some all purpose crud). I also disconnected the drain hose underneath but it looked pretty clear. Put everything back together, and the first time we used it, it did drain and we were hopefull. But the second time, it did not. But again, it worked on “cancel drain”.
ISTM from looking around a bit that the two main possibilities at this point are something wrong 1) with the control keypad, or 2) with the pump. The pump is cheaper, but also looks like more work (you need to disconnect and pull out the whole machine), but in any event, I’d like to only work on this one more time.
Could be a problem opening the drain. I assume there is a solenoid that controls that valve. The valve itself may be dirty, or electrical connections, or corrosion somewhere.
I don’t have a disposer. The d/w drains directly into the drainpipe below the kitchen sink (and the kitchen sink drains freely).
I did not disconnect the hose at the kitchen sink end. But I did blow into it at the d/w end, and was able to force the water in the hose down the drain. In addition, that hose is translucent white plastic, and it looks pretty clean from the outside.
If it drains properly when you push a certain button, but doesn’t drain properly when you push a different button, my money is that there’s something wrong with the buttons. I would continue to test it, just to be sure it’s actually different buttons that act different, and not just random chance that “cancel drain” seems to work better than the normal cycle.
However, and I say this as a person with a 15+ year old dishwasher, other parts are likely to give up the ghost sometime soon, and you may just do better with an all new dishwasher.