The short answer
Cold or wet dishes are usually incoming water temperature and rinse aid rather than a failed heater. A genuine heating fault shows as cycles that run long and finish with cold water in a machine that still washes.
What you find at the end
- Dishes cold and wet — Most often drying, which is rinse aid and heat together.
- Detergent left undissolved in the dispenser — The water was too cool for the tablet to dissolve.
- Plastics wet while china is dry — Normal behaviour; plastics hold water and cool quickly.
- Cycles running far longer than they used to — The machine waiting for a temperature it cannot reach.
- The tub is cold at the end of a hot program — Consistent with no heating at all.
- Not this fault: dishes are dirty rather than wet — Read the cleaning page.
Ranked for this class of machine
- Incoming water too cool — First, and free to test by running the tap hot first.
- Rinse aid empty or set too low — First for drying complaints, and the most misunderstood setting on the machine.
- Heater or heating element failed — Third, and it produces long cycles with a cold tub.
- Thermostat or sensor drifted — Fourth, and it can stall the cycle instead of ending it.
- Scale on the heating surface in a hard-water area — Fifth, and it slows heating rather than stopping it.
- Control not calling for heat — Last, and rare.
Check in this order
- Run the kitchen tap until hot, then start the machine — It removes the leading cause immediately.
- Check and raise the rinse aid setting — It addresses the drying complaint directly.
- Compare the cycle length with what it used to be — A stretched cycle is the signature of a real heating fault.
- Feel the door and the tub at the end of a hot program — Cold at the end, with a long cycle, points at the heater.
Owner checks
- Run the hot tap at the sink before starting a cycle — The machine then fills with hot water rather than pipe-cold.
About 5 min
- Fill the rinse aid reservoir and raise its setting — It is the main reason dishes come out dry.
Tools: rinse aidAbout 10 min
- Time a full hot program and compare with normal — The best owner-side evidence of a heating fault.
About 120 min
- Run a descaling cycle if the area has hard water — Scale on the heating surface slows everything.
Tools: descalerAbout 90 min
- Load plastics on the upper rack and expect them to stay damp — It removes a false symptom from the picture.
About 10 min
- Stop before reaching the heater under the tub — It is a mains-connected part in a wet enclosure.
Heat and water in a sealed box
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. Open the door carefully at the end of a hot cycle, because escaping steam scalds, and keep children clear at that moment. Never use a descaler and a bleach-based cleaner together.
When to call
Call when the incoming water is hot, rinse aid is present and the cycle still runs long and finishes cold, because the heater and its sensor are under the tub. Call as well if the machine stops mid-cycle with a cold tub, which usually means it is waiting for a temperature it cannot reach. On an inexpensive machine, ask for the price before authorising a heater repair.
Related pages
Scope
Generalized across dishwasher families under this badge rather than a model line; where a family-specific or model-specific page exists it is the narrower answer. Not here: heater ratings, sensor values, program temperatures, rinse aid settings by model and descaler product names.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
