Spray Arms

Examine the spray arms inside the dishwasher to make sure the holes in the spray arms are free and clear of debris. Your dishwasher should have several spray arms, including one at the bottom of the tub, one under the top rack, and possibly a third spray arm on the top of the tub. Sometimes food and mineral deposits can block holes in the spray arms, preventing water from spraying effectively. If this occurs, warm some white vinegar and pour it into a spray bottle. Spray the holes with the vinegar and dislodge debris with a toothpick or large safety pin.

Filters

Check to see if your dishwasher has clogged filters. Filters generally cover the drain valve area to catch debris as the water drains from the dishwasher. Many dishwashers have maintenance-free filters, but your dishwasher may have filters that need cleaning. Read your owner's manual before you perform any filter maintenance to avoid damaging your dishwasher.

Water Temperature

Check your water temperature to make sure it's hot enough. Water that is under 120 degrees Fahrenheit may not be hot enough to clean dishes effectively. Turn your kitchen hot water tap on and wait until the water warms up completely. Fill a cup and measure the water temperature with a kitchen thermometer. If the water is less than 120 degrees Fahrenheit, turn your water heater up to 120 degrees.

Loading

Load the top rack properly. Place cups and bowls upside down in the rack and don't nest dishes because this can prevent water from reaching dishes. Don't overload the top rack. Instead, position each item so the dirty areas of the dishes will receive full contact with water spraying up from the main spray arm located beneath the top rack. Prevent items from hanging below the top rack, which could prevent the spray arm from rotating.

Service

Call for service if your top rack dishes don't get clean after troubleshooting these areas. If your dishwasher is still under warranty, the manufacturer can give you instructions for obtaining warranty service.