The short answer
On a Foster dishwasher that is leaving dishes dirty, the cause to suspect first is filter and sump carrying old debris, with rinse aid empty behind it. The ranking below is written for the manual-filter build, which you can confirm in seconds: lift the lower basket and look at the sump: a removable cylinder and a flat mesh plate means the filter is yours to clean and nothing grinds debris for you. Arms, filter, dispenser, loading and programme are owner work; anything under the sump is not.
What you observe
- White cloudiness on glassware — Mineral film if it clears with a weak acid, etching if it does not.
- One shelf clean and the other dirty — A sector problem, which only a spray path can produce.
- 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.
- Food deposits redeposited on the upturned items — Debris coming back out of the sump, which is a filter story.
- 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 this brand
- Filter and sump carrying old debris — Ranked first here: the tell is a gritty film on everything rather than dirt in one place: a whole-load problem, evenly distributed, which points at the water rather than the spray.
- Rinse aid empty — Second: 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.
- Loading that shadows the spray — Third: water travels in straight lines.
- Scale and hard-water film — Fourth: it ranks here because the test is definitive: a cloudy glass that clears with a weak acid rinse is scale, and one that does not is etching, which is permanent.
- 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.
- Detergent type, dose or a blocked dispenser flap — Sixth: it ranks where it does because it is free to correct and because the dispenser is checked in the same motion as the spray arm above it.
Check in this order, and why
- 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.
- Check the rinse-aid reservoir — Empty, the load comes out spotted and wet even when it is genuinely clean.
- Reload with nothing nested and no tray on the outer edge — Water travels in straight lines, so anything shadowing is simply not washed.
What an owner can safely check
- Run the kitchen tap hot, then start the longest hot programme — Tests temperature and programme length together, on one load.
About 10 min
- Spin each spray arm by hand and clear any blocked jets — The fastest check on the list and the one that explains an uneven load.
Tools: cocktail stickAbout 10 min
- Reload with nothing nested and no tray blocking the spray — Water travels in straight lines; anything shadowed is simply not washed.
About 15 min
- STOP HERE if the wash sounds weak with everything above clean — Circulation is a pump question and it sits behind the sump.
Before you open anything
Safety
Switch the machine off at its spur or unplug it, and shut the isolating valve under the sink, before anything is opened — water and mains wiring sit close together under this cabinet. Never defeat the door latch to watch a cycle run with the door open; that interlock stops a hot spray at head height. Bail standing water out before tipping the machine, and expect glass in the sump, so feel with a cloth rather than bare fingers. Get a second person before you pull the cabinet out or tilt it.
When to call a technician
Call when the arms turn freely, the filter is clean, the water arrives hot, the load is sanely stacked and the result is still poor. At that point the question is whether the machine is developing pressure at all, and that is measured at the pump rather than guessed from outside.
Nearest pages of this class
What this page does not cover
Written for Foster dishwashers as a class, not for one family. No family-specific page for this brand and appliance is published here yet; where one exists for your unit it takes precedence over this page. Wiring colours, torque figures and part numbers are deliberately not here: they differ by family.
