Display shows E4; refrigerator may not defrost properly, leading to frost buildup on the evaporator.

Safety first: Unplug the refrigerator before removing the freezer evaporator cover. Use caution around sharp metal edges and ice.

Steps:

• Access evaporator: Remove freezer shelves and the rear panel to expose the evaporator coil.
• Locate the defrost sensor: The thermistor is typically clipped to the evaporator tubing or mounted near the top of the coil.
• Check placement: Ensure the sensor is firmly attached to the coil; a loose sensor can cause incorrect readings.
• Test sensor: Disconnect and measure resistance with a multimeter. Compare to the expected value for the coil temperature. Replace if open, shorted, or out of spec.
• Inspect wiring: Look for brittle or broken wires, especially where they pass through the cabinet.

Corrective action: Replace the evaporator thermistor if defective and reattach it securely to the coil. Manually defrost any heavy ice buildup with towels and gentle warm air (no open flame). Reassemble, restore power, and monitor operation.