If you don't put any dishes inside an automatic dishwasher and it still fills up with water, there could be a couple of reasons for this behavior:
Inadvertent Activation: Sometimes, the dishwasher can be accidentally turned on or triggered to start a cycle. This can happen if someone accidentally presses the control buttons or if there is an issue with the dishwasher's control panel. It's essential to ensure that the dishwasher is not in a demo mode or has any control panel malfunctions.
Sensor or Float Switch Issue: Dishwashers have sensors and float switches to monitor water levels inside the machine. If any of these components are malfunctioning, they may incorrectly signal the dishwasher to fill with water, even if there are no dishes inside. The float switch is a small device usually located at the bottom of the dishwasher that rises with the water level. If it gets stuck or becomes faulty, it can cause the dishwasher to think it needs water.
Filling for Rinse Cycle: Some dishwashers have a rinse-only cycle that runs a short cycle without detergent to rinse off any debris or food particles inside the dishwasher. This rinse cycle may activate even if there are no dishes inside the dishwasher.
Malfunctioning Water Inlet Valve: The water inlet valve is responsible for allowing water to enter the dishwasher during the wash cycle. If the valve is stuck open or faulty, it can lead to the dishwasher continuously filling with water, regardless of whether there are dishes inside or not.
Control Board Issue: The dishwasher's control board manages the various functions of the machine. A malfunctioning control board may send incorrect signals to the dishwasher, causing it to fill with water unexpectedly.
If your dishwasher is filling with water when it shouldn't, it's best to check for any obvious issues first, such as accidental activation or control panel problems. If everything seems normal, but the problem persists, it's recommended to contact a professional appliance repair technician to diagnose and fix the underlying issue. Tampering with or attempting to repair the dishwasher yourself can be dangerous and may void the warranty if the appliance is still covered.