Display shows E04 and the coffee maker shuts off shortly after starting; the exterior feels unusually hot.

Safety: Unplug the coffee maker and allow it to cool completely before opening.

• 1. Clean and descale:
  • Perform a full descaling cycle with a 1:1 vinegar and water solution to remove mineral buildup on the heater.
  • Run at least two full clean-water cycles afterward.
• 2. Inspect the temperature sensor:
  • Remove the bottom or rear cover to access the heater block.
  • Locate the NTC thermistor (small sensor clipped or screwed to the heater or warming plate).
  • Ensure it is firmly attached with thermal paste or a tight clip; resecure if loose.
  • Test the thermistor with a multimeter: measure resistance at room temperature and compare to typical NTC values (often 50–100 kΩ at 25°C). If it reads open or shorted, replace the sensor.
• 3. Check heater relay operation:
  • On the main control PCB, locate the heater relay.
  • Visually inspect for welded contacts or burn marks.
  • If the relay is stuck closed (heater always on), the unit will overheat and trigger E04. Replace the control board or relay module.
• 4. Verify ventilation:
  • Ensure the coffee maker is not placed in a confined space or directly under cabinets with no airflow.
  • Clean any dust or coffee residue from vents and openings.
• 5. Test operation:
  • Reassemble, plug in, and run a water-only brew cycle while monitoring for normal heating and no E04.