How can I mend my Diplomat APL 8215 dishwasher?

For the last few washes mu Diplomat APL 8215 has started leaking at the base of the door and it appears that it does not automatically stop filling with water. I can move the rotary programme switch on one click and the machine stops filling and drains normally until the next fill when it again does not stop filling and will leak.
What should I check and where may I find diagrams or plans of the machine?
Thanks in anticipation,
Keith