D/W won't drain. Last time, several months ago, I found the piston/nut in hideous condition. Replaced it. Flapper valve was fine. Unit worked great. Now it isn't draining again. I ran the test cycles and when I manually put it to the last step, draining, the drain pump runs and the tank empties perfectly. When a cycle runs it does not empty at all, just a little trickle. The difference between the two is the normal cycle, on drain, the main motor is still running and the solenoid pulls in. In the test cycle only the little drain pump is running and the solenoid is not energized. Thoughts? And, no, I have not checked the two valves (yet). What does the solenoid do? My guess is that with the main pump running maybe there is some pressure holding open the return valve from the collection chamber back into the tub?

I am not at home now and do not have the model # beyond what is listed. There most definitely is a second pump, unless I am confusing the main motor as being connected to a pump as well? To what else would this main motor be connected? When in the test modes, all mid-sequence steps that do a drain action, the main pump runs and the solenoid pulls in. There is little or no draining when this is going on. The very last step, the main pump shuts off, the solenoid is not pulled in and only the little drain pump runs. I have not measured to see if power is being applied to the small pump when these intermediate test steps are running.

Thanks, I think I am getting a feel for its operation. The small pump apparently is used to empty the sump out? That is the impression I am getting from what info I can find. When I do a 'test' run (rinse only) I haven't noticed the little pump coming on at the end (to empty the sump), which would be witnessed by a short burst of water in the drain. It seems logical that the small pump is indeed a 'boost' to get the flapper seated properly. I will have to pull the main pump off and see what I can find. I didn't see any actual timings in the tech sheet I pulled from under the tub. The only timings it listed were in the test modes. If the test modes are indicative of the actual cycle times, there were two drains in the middle that were I think 60 seconds and then the very final one, using the small pump, of 70 seconds. I am curious as to the 'circuitry' of the drain system. It looks like the small pump pulls from the sump right into the collection chamber. I guess this then forces the spring loaded collection valve shut and diverts to the drain port.