Dishwasher fills and circulates but does not heat; cycles run unusually long and end with E3 on the display.

Safety first: Disconnect mains power and close the water supply. Heating components operate at full mains voltage and can cause electric shock.

• Confirm symptom: Run a hot program and open the door briefly after 15–20 minutes (pause the cycle). If the water is still cold and E3 appears, the heater circuit is likely at fault.
• Check wiring connections: Remove the side panel (or base panel, depending on model) to access the flow-through heater assembly. Inspect the heater terminals and wiring harness for signs of burning, loose connectors, or corrosion.
• Test heater resistance: Using a multimeter (with power disconnected), measure resistance across the heater terminals. A typical SMEG heater is in the 20–30 Ω range. An open circuit (infinite resistance) indicates a failed heater.
• Inspect NTC sensor: Locate the NTC temperature sensor in the sump or heater housing. Check its connector and wiring. A sensor that is open or shorted will cause E3 and should be replaced.
• Control board check: If heater and NTC test good, the heater relay on the main PCB may be burnt. This requires board repair or replacement by a professional technician.