The short answer
A Caf ZDT dishwasher that leaves grit is telling you the spray is not reaching the soil. The matrix below carries a single model tag, so there is no revision fork to work around on this family: what holds for that tag holds for the line. Three checks — arms turning freely, filter clear, hot water at the tap before the cycle — settle most of these before any part is suspected, and they belong in that order on these models.
What you can observe on these models
- Cycle time has got noticeably longer — The control is extending the cycle to reach its target temperature, which points at incoming water temperature or the heater.
- Gritty residue on the underside of bowls and cups — Soil that was washed off and then redeposited, which means filtration rather than spray pressure.
- A white or cloudy film on glassware — Hard water and insufficient rinse aid. Permanent etching looks the same but does not wash off with a vinegar rinse.
- The top rack is noticeably dirtier than the bottom — The upper spray arm is not turning or is not being fed, so pressure is going to the lower arm alone.
- NEAR MISS — dirty water left standing in the tub — That is a drain fault, not a wash fault, and the drainage page covers it. Cleaning cannot be judged until the tub empties.
Causes, most likely first on this family
- Hard water and rinse aid — First when the complaint is film rather than grit: minerals left behind as the water evaporates coat everything equally, which no amount of spray pressure will change.
- Filter, sump and the drain path between cycles — Second, and the maintenance that most owners of these models have never been shown.
- Spray coverage — arms, holes and loading — Third: coverage problems show as patchy results, with some items perfect and others untouched, rather than as uniform film.
- Incoming water temperature and cycle selection — Fourth, and worth testing before any part is bought.
- Heating element or wash pump failure — Last: parts fail suddenly, and a suddenly cold or suddenly weak machine is the only case where they lead.
Check in this order, and why
- Compare the top and bottom racks after a load — A clean bottom with a dirty top isolates the upper arm feed and the diverter immediately.
- Reload the machine deliberately and run it again — Tall items, nested bowls and a blocked dispenser produce a dirty load on a perfectly healthy machine.
- Clean the filter, then run an empty hot cycle — This clears the sump and gives the next diagnosis a clean starting point.
- Listen through the wash for the diverter changing — A change in pitch as pressure shifts between arms is normal on this platform; a constant note is a reason to call.
Before you open anything
Safety
Kill power at the breaker before working in the sump — a capacitor can hold a charge after the power is off. Do not mix cleaning products in the tub: chlorine and acid descalers together produce gas in a closed cabinet. Run any descaler exactly as its label says, alone, on an empty machine.
Models in the ZDT family
Reference| Model number | Family key |
|---|---|
| ZDT98***N*** (v7) | caf:dishwasher:zdt |
When to call a technician
Cleaning the filter, clearing spray holes and correcting the detergent are yours to do as often as needed. Call once a part has to be condemned, or if the machine trips its breaker during the heated part of a cycle — that is an element or a wiring fault and it does not improve with use.
Other faults covered for this family
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
