A dishwasher spray arm needs clear openings to distribute water across the racks. Food particles and mineral scale can create weak spray patterns and leave dishes dirty.
Remove the arm safely
Turn the dishwasher off and take out the lower rack. Follow the appliance instructions for releasing the spray arm rather than forcing its retaining clip.
Inspect every opening
Hold the arm up to light and look for debris in the holes and center hub. Rinse it under the tap and use a soft brush for residue.
Do not enlarge the jets
Avoid sharp metal objects that can change the opening size. If scale is stubborn, use an appliance-safe cleaning method.
Reinstall and test
Spin the arm by hand to confirm it moves freely, then run a short cycle and check the spray pattern.