A dishwasher usually signals trouble before it stops. The signs are small and easy to miss, and most of them can be checked at the tub with no tools beyond a flashlight and a thin brush.
Water that stays in the tub
Open the door at the end of a cycle and look at the floor of the tub. Some water at the bottom is normal on many models. Water that pools, stays after the cycle, or rises during the fill is worth noting. Start with the drain path. Clear food debris from the bottom filter and the sump area, then run a short cycle and see whether the water leaves. Your model's manual shows where the filter sits. If the water returns after a clean drain, the pump or the drain connection needs a closer look.
A spray that slows or stops reaching the rack
Watch the spray arms during a full cycle. Hard water deposits and food particles clog the arm holes first. Lift the arms off their mounts, clear each hole with a thin tool, and rinse them under running water. If an arm turns slowly, sticks, or wobbles after cleaning, the bearing or the drive is wearing. Write down which arm it is and whether the problem repeats.
Glassware that clouds or comes out warm and not clean
A white film or spotting often comes from water chemistry, so check the softener setting and the rinse aid level first. Dishes that come out warm but still soiled point somewhere else. Ask whether the heating element and the water temperature sensor are being tested, not only the detergent. Those two parts decide whether the wash and rinse reach working temperature.
Sounds that change
A steady hum during the wash is normal. A grinding note, a rattle that moves around the tub, or a new whine at the start of the fill is a change worth recording. Note which phase of the cycle makes the sound. The phase often narrows the list of parts to check.
The door, the gasket, and the floor underneath
Look at the rubber gasket around the door for cracks, flattened spots, or food caught in the seal. Check that the door closes flush and that the latch engages without force. Water on the floor beneath the door is not always coming from the door, so look at the supply line and the drain hose as well before you assume the source.
Keep a short record
Write down what you saw, which cycle you ran, what you cleaned, and what you changed. Put the install year next to the notes. Age is a planning input. When the same signs keep returning, the planning window for a replacement moves closer, and the notes make that clear to anyone you call. The dishwasher page on this site lists typical service life and shows how to turn an install year into a planning date.
What to ask before anyone opens the tub
Ask which part the technician thinks is failing and what evidence points to it. Ask whether the part is still supplied for your model and what the repair would cost compared with a replacement. If a service plan is in place, ask what it covers for this particular problem, and read the written terms rather than relying on what was said on the phone. Ask what is left for you to do after the visit, such as cleaning the filter or keeping the notes going. For a broader view of how dishwashers compare with other appliances on service life, the appliance ranking on this site is a useful next read.