Here's another easy test to try to see if it is getting too much water. Run a Normal cycle with the sink hot water open half way as you did before, then after the third fill (the high fill), open the door and note how high the water level is in the tank. Close the door, then open your water valve all the way and let the dishwasher continue to the 4th fill, which is another high fill. Again after 90 seconds, open the door and see how high the water level is this time. If during this fill you hear the float switch stopping the water before the 90 seconds is completed, open the door immediately and verify that the high water level is causing the float switch to trigger. If this happens, you are getting too much water with your valve open all the way, and you'll need to find some way to restrict the water flow to prevent this from happening when the dishwasher gets permanently installed.