kenwood dishwasher kdw60s12 top spray arm not spinning?

If you can spin the spray arm by hand then it's OK

The rinse water will have little bits of crud in it - food debris and bits of limescale - unless it drains off properly the drying process will bake it on hard.

Consider a dishwasher cleaning product.
Rinse off the worst of the food debris before loading the machine
Above all - use good quality liquid rinse aid - to let the water drain off properly.

Good luck...

M Berry
October 2014