Accidentally placing a large pan in the bottom rack of the dishwasher that blocks the upper spray arm from rotating may cause some issues, but it is unlikely to cause significant harm to the dishwasher itself. However, it can impact the dishwasher's cleaning performance.
When the upper spray arm is blocked, it restricts the water flow and reduces the ability of the dishwasher to effectively clean the dishes on the upper rack. The dishes in the upper rack may not receive adequate water and detergent coverage, resulting in less efficient cleaning.
It's important to note that dishwashers are designed with safety features to prevent severe damage in such situations. Modern dishwashers typically have sensors and mechanisms that detect obstructions and can pause or change the cycle to avoid any potential harm.
To ensure optimal cleaning performance and prevent potential issues, it is best to avoid obstructing the spray arms in the dishwasher. Always arrange your dishes and utensils in a way that allows free movement of the spray arms, ensuring adequate water and detergent distribution throughout the dishwasher's cleaning cycle.