Our Western Appliance Repair technicians run into a lot of unusual appliance service calls. Here in this picture you will see a small mushroom looking object in the lower right side of the picture. This device is float switch sensor, also called an overflow sensor.
Most dishwashers will fill with water for a programmed duration. This duration is not failsafe though. Many homes have higher water pressure as compared to others. Higher pressure will lead to more water in the tub. How do the designers compensate for this? Use a float sensor. In homes with high water pressure the float sensor will shut off the water before the programmed duration is completed if the water rises to a specified point. If the dishwasher has low water pressure then the programmed water fill duration will shut off the inlet valve when duration is complete.
This floating piece of plastic has a shaft on the bottom of it which triggers a shutoff switch if water gets too high. Sometimes these float sensors will get stuck in the “up” position and won’t allow water to enter the dishwasher at all.