Display shows F4 and the wine cooler may shut down cooling or run continuously; defrost may not operate correctly.

Safety first: Disconnect mains power before accessing the evaporator or control board. Beware of sharp fins and hot components.

F4 is commonly associated with defrost system issues in Miele wine coolers.

• 1. Access evaporator and defrost components:
  • Remove shelves and interior rear panel to expose the evaporator.
  • Locate the defrost heater (usually a metal or glass-encased element at the base or woven through the evaporator) and the defrost sensor.
• 2. Visual inspection:
  • Check for heavy ice buildup on the evaporator, which indicates defrost failure.
  • Look for burnt or broken heater sections and loose sensor clips.
• 3. Test the defrost heater:
  • With power off, disconnect heater leads.
  • Measure resistance; a typical heater will show a finite resistance (e.g., 50–300 Ω). An open circuit means the heater is bad.
• 4. Test the defrost sensor:
  • Disconnect the sensor and measure resistance at room temperature.
  • Compare to expected NTC values; open or shorted readings indicate failure.
• 5. Replace faulty components:
  • If the heater is open, replace with the correct Miele defrost heater assembly.
  • If the sensor is defective, replace with the specified Miele defrost/evaporator sensor.
• 6. Check wiring and board:
  • Inspect wiring from heater and sensor to the control board for burns or breaks.
  • If components and wiring are good, the defrost relay or control board may be faulty and should be replaced by a technician.
• 7. Manually defrost: Before reassembly, fully defrost the evaporator by leaving the unit unplugged with doors open and towels in place until all ice is gone.