If your dishes are still dirty after running the dishwashing cycle, first make sure you're loading them correctly. Our how to load a dishwasher video gives tips on where (and where not) to load dishes to get them clean.
Other non-mechanical reasons for dishes not getting clean include water temperature and water hardness:
It's also important to use the right amount of detergent for your water's level of hardness. This video shows how to check water hardness. Use more detergent if your home has hard water.
Poor cleaning could also be due to a mechanical problem with your dishwasher.
Dishes won't get clean if the detergent dispenser doesn't open. Watch our troubleshooting video for tips on how to fix a broken detergent dispenser.
Check the spray arms for clogs, jams or breaks and clear clogs or replace damaged spray arms that can prevent dishes from getting clean. Some dishwashers use a diverter motor to control the water supply to the upper spray arms. If just the dishes in the upper dishrack aren't getting clean, you may need to replace the diverter motor in that type of dishwasher.
Problems with the dishwasher circulation pump can also prevent dishes from getting clean. Clean the upper pump assembly and the sump area to get the best water flow through the spray arms. You may need to replace the dishwasher circulation pump and motor assembly or pump motor if cleaning the pump doesn't restore water flow to the spray arms. Watch our repair guide video for replacing the circulation pump in a dishwasher if the pump needs replacement. Our dishwasher not cleaning dishes video provides additional troubleshooting tips to help you get the best cleaning results from your dishwasher.