Recently our dishwasher stopped effectively washing dishes. I've gotten intimately familiar with it over the last two weeks disassembling and reassembling it and my wife is starting to talk replacement... I don't accept this solution yet.

Water fills properly and the cycle starts out strong. I've verified that both the lower and upper wash arms rotate and spray. Heating element works fine (I burned my arm twice working on the damn thing, it's like playing Operation).

The problem comes around 30s-1m into the wash cycle. The audible pitch of the motor changes slightly and then I hear a light thump which I believe is the check ball settling into 1 of 2 positions, after which time the pressure drops to everything and I get no spray on any arms. If I open the door, wait 15 seconds and restart, I once again get some spray from the arms but then the same thud happens and spraying action stops.

I've pulled the volute cover off and verified that the check ball moves freely and that the pump impeller spins freely and all ports are clear of debris. I also drained the entire system, pulled the sump out and ran the wash motor dry after inspecting it for debris. It runs fine but I did notice is that every now and then there is some light plastic on plastic friction that causes a squeal, but this is not all the time, had no noticeable affect on RPM, and eases up when wet.

I honestly can't say that I understand what controls the check ball checking the port to the lower arm versus the upper arms, seems like the design would make it tough to guarantee an exact exposure time per lower vs upper. But I guess that's neither here nor there.

So I'm at a loss. All systems seem to be in tact, when I'm getting flow to the arms they spray and rotate freely and do their job. But I just cannot figure out why my flow is dropping out.

Any advice would be appreciated.