It sounds like there could be a blockage in the water feed to the lower part of the washer. Have you tried a dishwasher cleaner. We had a problem with our Bosch dishwasher not heating up a couple of years ago and when the engineer tried it, it worked fine. He advised using a dishwasher cleaner every 3 months. We took his advise and never had a problem with it repeating this problem since.
Ian, March 2009