How a Drain Float Switch Works on a Dishwasher

Identification

• The float switch always sits in the bottom of a dishwasher’s tub, but the exact location inside the tub varies from model to model. On some dishwasher models, the float switch has a domed cover. If the dishwasher float switch does not have a cover, it is usually a device that sits on a post that it moves up and down. The shape of the float varies depending on the dishwasher model.

Measuring Water Level

• The float switch moves up and down with the water level inside the dishwasher’s tub. Once the water level inside the tub reaches a predetermined level, the float triggers a switch on the post, signaling to the dishwasher that the water level has reached the needed amount. The dishwasher then heats and sprays the water inside the dishwasher with the spray arm. The float measures the water level once the dishwasher’s drain opens to let the water out of the machine, indicating when the water level drops all the way down.

Inlet Valve

• The float switch has an electrical connection to the inlet valve on the underside of the dishwasher’s tub. The inlet valve regulates the flow of water into the tub. When the float switch reaches the high-water mark, it sends an electrical pulse to the inlet valve, which in turn shuts off the flow of water to the tub. If the dishwasher’s tub starts to overflow, the problem could be a loose connection on the inlet valve or a bad inlet valve.

Food Debris

• Over time and use, the float switch or its cover may become caked with food debris. This debris can dry and harden, causing the float switch to stick on its post or not allowing the float switch to rise or fall below a certain level. You must remove the float switch’s cover, which can involve removing the screw that holds the cover in place, and then scrub the float switch and its cover with a toothbrush.