The short answer
On the COSDWH family the usual reason a Cosmo dishwasher is leaving dishes dirty is loading that shadows the spray, and that is where the order below departs from the brand-generic article one level up: on the compact or slimline build it outranks filter and sump carrying old debris. A narrower cabinet or a countertop unit means a smaller sump, less water in the wash and far less tolerance for a heavy load. Arms, filter, dispenser, loading and programme are owner work; anything under the sump is not.
What you observe on these models
- Greasy film that wipes off with a finger — Heat rather than mechanics: fats need temperature to move at all.
- Dishes clean but soaking wet at the end — A drying complaint rather than a cleaning one, and rinse aid is the first thing to check.
- One shelf clean and the other dirty — A sector problem, which only a spray path can produce.
- Food deposits redeposited on the upturned items — Debris coming back out of the sump, which is a filter story.
- Gritty film on everything in the load — Evenly distributed, which points at the water being dirty rather than the spray being blocked.
- NEAR MISS — water standing in the sump at the end — That is a drainage fault, and the drainage page is the right one to read.
Causes, most likely first on the COSDWH family
- Loading that shadows the spray — Ranked first here: it ranks first on a compact machine because the margin is smallest there: less water, a smaller sump and no room for a load that fights the spray.
- Filter and sump carrying old debris — Second: the wash water is recirculated, so the filter is the only thing standing between last night's debris and tonight's plates. Once it is loaded the machine is washing with dirty water and redepositing what it removes.
- Spray arms blocked or not turning freely — Third: everything the machine does, it does with two or three spinning arms.
- Incoming water not hot enough — Fourth: detergent needs heat to work and fats need heat to move.
- Weak circulation from the wash pump — Fifth: if the arms turn freely, the filter is clean, the water is hot and the load is sane, then the remaining question is whether the machine is developing any pressure at all.
- Rinse aid empty — Sixth: rinse aid is what makes water sheet off rather than bead, and without it the load comes out spotted and wet even when it is perfectly clean.
Check in this order, and why
- Reload with nothing nested and no tray on the outer edge — Water travels in straight lines, so anything shadowing is simply not washed.
- Lift out the filter and look at the sump beneath it — A loaded filter means the machine is washing with dirty water and redepositing it.
- Spin each arm by hand and look through the jets — Seconds to do, and it is the only cause that produces one clean shelf and one dirty one.
Before you open anything
Safety
Power off at the spur, water off at the valve, then open anything. Those two come first because the wiring and the plumbing in this cabinet run alongside each other. Leave the door latch alone: defeating it lets a hot cycle run with the door open. Bail the water out before you tip the machine forward, and treat anything in the sump as sharp until you have seen it.
Models in the COSDWH family
Reference| Model number | Family key |
|---|---|
| COS-DWH240TT*** | cosmo:dishwasher:cosdwh |
When to call a technician
Bring someone in once a full hot programme on a correctly loaded machine with a clean filter still leaves food on the dishes. Call sooner if the wash sounds obviously weaker than it used to, because a failing circulation pump gets worse rather than better and it takes the heater element with it on some machines.
