LG Dishwasher Not Cleaning Properly: Causes & Fix

Dirty Dishes Start at the Spray Arms and Filter#

Poor cleaning is usually a water-delivery problem, not a broken machine. The dishwasher has to spray hot water hard through clear arms and keep the recirculating water clean via the filter; when either is compromised, dishes come out with residue even though the cycle runs normally.

Ranked Causes on LG Dishwashers#

Clogged spray arms lead because their small jets catch food and hard-water scale, and once blocked they can't blast the dishes clean — the top rack usually suffers first since it's fed last. A clogged filter is the close second: when the filter packs with food, the recirculated water is dirty and redeposits grit onto the dishes.

A fouled turbidity sensor misreads how dirty the water is, so the machine may run a shorter or lighter cycle than the load needs. A degrading inverter direct-drive motor weakens the wash action, and water that isn't hot enough — LG cleaning relies on water reaching roughly 140–155°F during the main wash — leaves detergent undissolved and dishes filmy.

What You Can Clean Yourself#

Start with the two big causes. Pull the lower and upper QuadWash spray arms — they typically unclip or unscrew — and clear each jet with a toothpick or thin wire, then rinse them out and refit them so they spin freely. Next, remove and clean the filter assembly at the tub floor: rinse the mesh and cup under running water to clear trapped food. Between them, these two cleanings resolve the large majority of poor-cleaning complaints.

Also confirm the incoming water is hot — run the kitchen tap hot before starting a cycle so the dishwasher isn't filling with cold water, and keep rinse aid topped up. Beyond cleaning, the turbidity sensor and the wash motor are internal repairs a technician handles if cleaning doesn't restore results.

Why Maintenance Fixes Most of These#

Poor cleaning is one of the few dishwasher complaints where the odds strongly favor maintenance over repair, and understanding why keeps you from replacing parts you don't need. The machine cleans by driving hot water hard through the spray-arm jets and recirculating it through a filter that keeps the water clean between passes. Both of those are consumable in the sense that they gradually foul: the jets collect food particles and hard-water scale that narrow the spray, and the filter packs with the food it's meant to catch until the recirculated water is dirty enough to redeposit grit. Neither is a failure — it's accumulation, and it's reversed by cleaning rather than parts. That's why clearing the spray arms and filter resolves the large majority of "not cleaning" cases, and why doing it every few weeks, along with keeping the inlet water hot and rinse aid full, prevents most of them from recurring. Only when a clean machine still under-cleans do the turbidity sensor and wash motor come into question.

Getting It Fixed#

Clearing the spray arms and filter fixes most cases; a sensor or motor needs service. Book a diagnostic and we'll confirm whether cleaning is enough or the sensor or motor is behind it.