Dishwashers conveniently take care of dirty dishes with minimal fuss and without having to get your hands wet. There may be times, though, when the convenience is overshadowed by the presence of black spots and specks from the appliance that, in turn, can leave the dishes looking spotty. Chances are the trap needs to be cleaned out, a DIY job that should remedy the situation.
Unplug and empty the dishwasher completely, remove the racks and set them aside. Spray the interior with a non-toxic commercial spray-on cleaner over visible spots and specks and allow it to set undisturbed so that the chemical can loosen the black spots for ease of cleaning. Consult the product packaging for directions on how long you should let it set. Wipe away the chemical with a dry and clean cloth; if the spots and flecks remain, try using a soft-bristled scrub brush for more friction. This should remove the spots.
Consult the manual that came with your particular brand and model of dishwasher. If none is available, perform an online search at the company's website; you're looking for the location of the solid's filter in the washer's drain basin, where smaller food particles not washed away during the pre-rinse cycle accumulate. Even if you pre-rinse dishes in your sink, tiny particles, such as coffee grounds, have a tendency to collect over time; and when the filter is clogged, a back flow pushes the particles outward and onto your dishes and into the washer's interior.
Use a Phillips head screwdriver to loosen the screw or screws that anchor the spinner to the bottom of the washer's basin -- it's the flat part that resembles a helicopter blade. Pull up and remove the spinner and you should see a flat grille screen. This is the cover for the solids filter. Either use the screwdriver to remove the cover or locate a locking push-tab to pop the cover off.
Look into the filter's trap and you'll more than likely see the culprit: caked-on food particles that are clogging the rinse holes in the filter, obstructing water flow. Scoop out the particles and debris, either with your hand or a plastic spoon. Remove as much debris as you can. Replace the cover, spinner and racks then run the washer empty so that the water pressure can push the remaining particles down the drain. It's best to use your machine's hottest water cycle.