We have a whirlpool dish washer(GU1500XTLQ0) that is around 4 years old. The top shelf seems to not be cleaning. I ran it with the door partly open and can see it is getting water up the arm. I tooy out the arm and it is not blocked and spinns freely. The very top spinner gets no water out of it. Could the pump not be pumping enough water to get pressure? Could it be blocked before the up tube in the pump itself?

Rob

Did you take a toothpick and clean out every one of the water holes in the top arm? My Maytag used to do this and when I cleaned out every hole it worked fine.