Diplomat dishwasher leaving detergent tablet undesolved?

My diplomat machine has been making quite a row when switched on. After the wash cycle the dtergent tablet is partially desolved, the crockery and cutlery is clean. it seems as if the machine when pumping water is full of air. presumably there is in sufficient water flow? can anyone throw any light as to the problem and how to repair?

Corky63
November 2010