Freezer or fridge not defrosting properly; heavy ice on back wall; display shows E4

Safety warning: Unplug the appliance before accessing the freezer evaporator area. Sharp metal edges and ice can cause injury; wear cut-resistant gloves.

Steps to diagnose:

• 1. Manually defrost: Empty the freezer, unplug the unit, and leave the door open for several hours or overnight until all ice melts. Place towels to catch water. This may temporarily restore cooling but does not fix the root cause.
• 2. Access the evaporator: Remove drawers and the inner rear panel of the freezer to expose the evaporator coil and defrost components.
• 3. Locate the defrost sensor/thermostat: It is usually clipped to the evaporator tubing or mounted on the evaporator frame. It may be a small round thermostat or an NTC probe.
• 4. Inspect and test: Check for broken clips, corrosion, or loose connectors. With the unit unplugged, disconnect the sensor and measure resistance. For an NTC, compare to expected values; for a thermostat, check continuity when the sensor is cold (placed in ice water). Replace if readings are out of spec or open when they should be closed.
• 5. Wiring check: Inspect the harness from the sensor to the control board for damage. Repair any broken wires and ensure connectors are fully seated.
• 6. Board consideration: If the sensor and wiring are good but E4 returns after a few days of operation, the control board may not be initiating defrost correctly and may need replacement by a professional.

Important: Do not chip ice off the evaporator with sharp tools; this can puncture the refrigerant circuit and render the appliance irreparable.