Kenwood KDW12ST3A not washing lower level

Hi. Firstly I wanted to say a big thanks for the help you gave me about 4 years ago to fix my Servis washing machine and supply the parts at great reduction. The machine is still going strong and not adding to landfill.

I now have a dishwasher problem I’m hoping for some help with please. It is working and I have not changed the way the pots are stacked inside but the bottom level is no longer washing properly from underneath. The details are:

– Plates on bottom mostly cleaned well
– Underneath of pots left dirty – eg bowls if placed upside down
– Top level is washing very well.
– If the door is opened mid cycle, the lower spinner doesn’t appear to have moved.

So, I think any washing effect is from the top spinner only, and there is no water coming up from the bottom spinner, or not enough for it to spin. I have checked:

– Spinner is not clogged up – have removed and poured water through all holes
– Nothing is obstructing lower spinner
– Filters are all clean
– Feeder pipe to lower spinner isn’t blocked at the spinner end of the pipe (inside the dishawasher)

Is there just one pump on this model, with a splitter feeding to two spinners? I’m thinking I might need to check for blockages at the splitter/pump end but am not sure where to find this.

Any help/guidance very much appreciated.
Serial number is 650 S/N 002141 in case that’s useful.