A dishwasher that runs a full cycle but leaves food, film, or grit behind is rarely broken — most of the time it's starved of one of the three things it needs to clean: a clear filter, freely spinning spray arms, and hot water. Most of these you can fix yourself in a few minutes. Here's the order a tech checks them.
Most modern dishwashers have a removable filter in the bottom that traps food. When it packs with gunk, dirty water just recirculates onto your dishes. This is the single most common cause of poor cleaning.
Check it: Twist out the cylindrical filter in the floor of the tub, rinse it under the tap, and scrub it with a soft brush. Do this monthly and cleaning improves dramatically.
The spray arms have small jets that can clog with hard-water scale, seeds, and debris. If a jet is blocked or an arm can't spin freely, whole sections of the rack never get sprayed.
Check it: Pop off the spray arms (usually a twist or clip), poke each jet clear with a toothpick, and make sure they spin freely by hand. Also check that tall items aren't blocking them.
Dishwashers need about 120°F water to dissolve detergent and cut grease. If the incoming water is cold — a common winter problem — detergent won't activate and dishes come out filmy.
Check it: Run the kitchen sink hot for a few seconds before starting the dishwasher so hot water reaches it right away, and use the "heated" or "sanitize" option.
Mineral scale coats the tub, jets, and heating element over time, and skipping rinse aid leaves spots and film. Both look like "not cleaning" even when the machine is mechanically fine.
Check it: Keep the rinse-aid dispenser filled and run a dishwasher cleaner or a cup of vinegar through an empty hot cycle monthly.
The wash pump pressurizes the spray arms and a chopper grinds food fine enough to rinse away. When either wears out, spray pressure drops and cleaning suffers even with a clean filter.
Check it: If the filter, arms, and water temp are all good and dishes are still dirty, this is the tech diagnosis — a pump or chopper repair.
Almost always repair — the top causes are free or a cheap part, and even a wash-pump job is well under the cost of a new dishwasher plus installation. Replacement only makes sense on a very old unit facing a pump failure plus other issues.
In Middle Tennessee or the Baton Rouge area? We'll come to you, same-day. Anywhere else in the U.S.? Send a 10-second video, a real technician tells you exactly what's wrong for $50 (credited toward the repair), and we ship you the exact part. 24/7 — text, call, or upload anytime.
The top rack is usually fed by the middle spray arm — if its jets are clogged or it can't spin, or the top rack's water supply tube is blocked, the top comes out dirty while the bottom is fine. Clear the arms and make sure nothing blocks them.
Gritty means a clogged filter recirculating food; filmy usually means water that's not hot enough, no rinse aid, or hard-water scale. Clean the filter, pre-run hot water at the sink, and keep rinse aid filled.
Most of the time it's free (filter/arms/water temp) or a low-cost part. A wash-pump repair is around $130 flat labor plus the part, and your $50 Quick Check credits toward it.