The short answer
On a built-in machine of this generation the filter is manual, it is not self-cleaning, and it is the first thing to lift out. Ranked first on this platform: A blocked filter. The checks below follow that ranking, and the first of them need no tools and no panel removed.
What you observe
- A gritty film on everything, worst on the lower rack — Redeposited soil is what a blocked filter looks like.
- Some items are perfectly clean and others in the same load are untouched — A pattern across the rack is a coverage problem.
- A greasy film on everything rather than gritty deposits — Grease left behind is a temperature symptom; grit is a filter one.
- NEAR MISS — everything is clean but wet — A drying complaint points at rinse aid and the final rinse temperature rather than at the wash.
Causes, most likely first on this platform
- A blocked filter — The filter in the base catches the soil the machine washes off, and the wash water is pumped through it continuously. It ranks first on this platform because the wash water is pumped through the filter continuously, so once it loads the machine is recirculating dirty water at reduced pressure — it puts the soil back on rather than taking it off, which is exactly what owners describe.
- Blocked spray-arm jets — Every hole in the spray arms is a jet, and they clog with grit, seeds and scale. It ranks second here because a cabinet of this vintage has wear on everything at once, which changes the ranking: the parts that wear are far more likely than the parts that break.
- Water arriving too cold — Detergents need heat to work. It comes third in the order — a genuine cause here, behind the ones above it on frequency alone.
- Detergent that is old, wrong or not released — Detergent absorbs moisture and loses its power on the shelf, and a dispenser flap held shut by a tall item never opens at all. It comes fourth in the order — a genuine cause here, behind the ones above it on frequency alone.
Check in this order, and why
- Lift the filter out of the base and look at it — Free, thirty seconds, and it is the most common cause by a distance. It leads because it tests the top-ranked cause.
- Spin each arm by hand and look through the jets against the light — Both checks take a minute and need no tools. Tests the second-ranked cause.
- Open the door mid-cycle and feel the steam and the water — A cold cycle is obvious the moment you open the door. Tests the third-ranked cause.
What an owner can safely check
- Twist out the filter, rinse it under a tap with a soft brush, and refit it locked — Check the coarse screen under it as well, and mind the glass.
Tools: soft brush, gloveAbout 15 min
- Take the arms off, clear each jet with a cocktail stick, and rinse them through — Most arms unclip or unscrew by hand.
Tools: cocktail stickAbout 20 min
- STOP here if the next step needs a meter on live terminals or a sealed panel off — That is where an owner check ends. Write down what each check showed and hand it to the technician.
Before you open anything
Safety
Unplug the machine or switch off its breaker before removing any panel, and close the supply valve before disturbing a fitting.
When to call a technician
Call when the filter, the arms, the loading and the detergent have all been eliminated and the machine still washes badly, because what is left is the wash pump or the heater and both are measured.
Nearest pages of this class
What this page does not cover
This page is written for the Moffat dishwasher as a class, not for one family or one model line. Where a family- or model-specific page exists for your unit, that page is the more specific answer and the one to read first. Deliberately not here: part numbers, wiring colours and disassembly order, which differ by family.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
