Most of us think of dishwashers as cleaning our dishes, but you should routinely clean your dishwasher, as well — especially if you’ve noticed a change in its performance. (I’m a huge advocate for performing regular maintenance on your appliances, just as you would your car, to maintain the life and — therefore — get the most out of your investment.)
Dishwasher detergent and food residue might buildup over time (especially if you use too much dishwasher soap and pre-rinse your dishes, which can leave white film on dishes). Clean out the filters and scrub the spray arm nozzles with a toothbrush to loosen any food residue clogged inside.
Then, the real secret of how to clean dishwashers is hiding in plain sight of your own cupboard: white vinegar.
Fill a cup with vinegar and put it in the top rack of the dishwasher (don’t add any soap to the dishwasher dispenser) and run the dishwasher as normal. Voila!
If you don’t have any vinegar (or the smell grosses you out), my brother swears by powdered citric acid in the dishwasher soap dispenser, and I’ve also heard of people successfully cleaning the dishwasher using Tang in the detergent dispenser.