When a dishwasher stops getting dishes clean, the first instinct is to blame the detergent and buy a different brand. Sometimes that's the answer. More often the machine isn't getting enough hot water to the right places, and no detergent fixes that. What's left on the dishes tells you a lot about where the problem is.
Read what's left behind
- Food stuck in one area, such as the top rack or one corner of the bottom rack: a clogged or blocked spray arm feeding that area.
- Grit or specks spread across everything: dirty water being sprayed back on the dishes, usually from a clogged filter.
- A white or cloudy film: either mineral and detergent residue or permanent etching of the glass. More on telling them apart below.
- Greasy film, dishes barely warm at the end: the water isn't hot enough, from the supply, the dishwasher's heater, or both.
- Detergent pod still whole, or powder caked in the cup: the dispenser didn't open, or it opened into a cold or dry wash.
- Dirty water standing in the bottom after a cycle: a drain problem, which also leaves dishes dirty because the wash water never fully clears.
Cloudy glasses: residue or etching?
Soak a cloudy glass in white vinegar for a few minutes, then rinse it. If it comes out clear, the film was mineral or detergent residue, and rinse aid, the right amount of detergent and a clean filter usually solve it. If it stays cloudy, the glass is etched, which is permanent damage to the surface. Etching is often linked to too much detergent in soft water or very hot washes. Using less detergent can keep it from getting worse.
Mineral film depends on your water. Charlotte Water, like other public water systems, publishes an annual water quality report, and that is the reliable place to look up your hardness rather than guessing.
Checks you can make
Turn the dishwasher off at its breaker or switch before reaching under the lower rack or removing the kick plate.
- Clean the filter. Most dishwashers sold in recent years have a manual filter at the bottom of the tub, under the lower spray arm. It twists out. Rinse the coarse and fine screens under the tap with a soft brush. If it hasn't been cleaned in a long time, expect an unpleasant surprise. The owner's manual gives a cleaning interval.
- Clear the spray arms. Spin each arm by hand; it should turn freely. Remove them (most clip or unscrew off) and rinse the holes, using a toothpick to push out seeds, glass chips or scale. Don't enlarge the holes.
- Check the loading. A tall pan, cutting board or the handle of a utensil can stop an arm from turning or block the detergent door. Spin the arms by hand after loading.
- Run the kitchen tap hot first. If your water heater is at the far end of the house, the dishwasher's first fill may be cold. Run the sink until the water is hot, then start the cycle.
- Use fresh detergent, stored dry. Powder and pods absorb moisture and clump. In a humid summer, a box kept under the sink or in a garage pantry can go off before you've used it up.
- Fill the rinse aid. It helps water sheet off dishes and helps drying a great deal, especially on models that don't use a heating element to dry.
Watch a cycle
If the simple fixes don't help, open the door about ten minutes into a normal cycle (the machine pauses when unlatched) and look:
- Is there water in the bottom? It should cover the area around the filter. A low fill points to the inlet valve, a clogged inlet screen, or a partly closed supply valve under the sink.
- Is it hot? Carefully check with your hand near the water, not in it. Lukewarm water suggests the heater or the thermistor that controls it isn't working, or the supply is cold.
- Has the detergent door opened? If it hasn't by the main wash, the latch or the dispenser actuator may have failed.
- Were the arms spraying? You'll hear a steady swish during a normal wash. A hum with no splash can mean the circulation pump has failed or is blocked.
Parts that cause poor cleaning
When the filter, arms and water supply are all fine, the remaining causes are mechanical or electrical:
- Circulation pump and motor: pushes water through the arms. A weak pump makes for a weak wash.
- Water inlet valve: a valve that sticks partly closed under-fills the tub.
- Heating element and temperature sensor: heat the water during the cycle; when they fail, washes run long and dishes stay greasy.
- Diverter or wash-arm switching: many models alternate water between arms; a failed diverter starves one arm.
- Drain pump: if wash water isn't pumped out, the rinse uses dirty water.
These need testing with a meter and access under the tub, which means pulling the dishwasher out of its cabinet on many installations. That's where a technician comes in.
Repair or replace?
A dishwasher that's otherwise in good shape is usually worth repairing for a pump, valve, heater or dispenser. If the tub is rusting through, the door is leaking from the frame, or the control board has failed on an older machine, replacement may make more sense. We'll tell you plainly if a repair isn't worth it.
A technician comes to the house, runs the dishwasher to see the fault, explains what failed and quotes the repair before any work starts. See our dishwasher repair service for what we handle. Bosch owners can go to Bosch dishwasher repair, and if you have a GE, see GE dishwasher repair.
Frequently asked questions
Should I rinse dishes before loading them?
Scrape off food scraps, but you don't need to rinse plates clean. Many modern detergents are formulated to work on food soil, and the dishwasher's sensors use how dirty the water is to set the cycle. Heavy pre-rinsing can make the machine choose a lighter wash.
Do dishwasher cleaning tablets fix poor cleaning?
They can help remove grease and mineral buildup from the tub and spray arms, but they won't fix a clogged filter, a failed pump or a bad heater. Clean the filter by hand first.
Why are my dishes still wet at the end of the cycle?
Plastic items stay wet on almost every dishwasher, since plastic doesn't hold heat. If glass and ceramic are wet too, check the rinse aid first. If that's full, the drying heater, the vent or the control may be at fault, depending on how your model dries.
Why does my dishwasher smell bad?
Usually a dirty filter or food trapped in the sump. Clean the filter, wipe the door gasket and the bottom edge of the door, and run a hot cycle with the machine empty. A smell that persists may mean standing water from a slow drain.