How to Test the Float Switch
When the water in the tub lifts the float to a set point, the float switch is triggered and it shuts off the water inlet valve, stopping the flow of water. If the float switch is defective, the tub may overfill.
To access the float switch remove the lower panel located beneath the door. The panel is usually held in place with two screws either above or below the panel. It may be necessary to first open the door to the dishwasher to reach the screws over the panel, then close the door to remove the panel.
Note the location of the float in the dishwasher's tub and you will find the float switch beneath it in the access area. The switch has two wires connected to it. Label the wires and connections so that you can properly reconnect them later. The wires are connected with slip on connectors. Firmly pull the connectors off of the terminals (do not pull on the wire itself). You may need to use a pair of needle-nose pliers to remove the connectors. Inspect the connectors and the terminals for corrosion. If either is corroded they should be cleaned or replaced.
Use a continuity tester or multitester to test for continuity. Set the multitester to the ohms setting X1. Touch one probe to each terminal. You should get a reading of either zero or infinity. With the probes still in place, depress the button or lever on the switch and the reading should change to the opposite extreme.
If the switch fails either test, it should be replaced.