This is a 12 year old Kenmore, but my experience applies to many dishwashers. The machine had run for almost a year without being cleaned. I found parts had failed from age and water passages were jammed with hard-water deposits and pieces of food, labels, etc. that had gotten past the filters. I cleaned out what I could and replaced parts that could not be cleaned or were damaged. Dishwasher now works better than it has for years. The work, including ordering parts, took about 4 hours, but this beats the alternative of spending abt. $600 n a new dishwasher.