Diagnostics show E4; heavy frost on evaporator, poor cooling, or frequent defrost issues.

Safety first: Unplug the refrigerator before accessing the evaporator and heater. The heater and metal edges can be hot or sharp.

Steps to resolve:

• Inspect frost pattern: Remove the freezer rear panel. If the evaporator is a solid block of ice, defrost is not working.
• Manual defrost: Unplug the unit and allow all ice to melt (towels and pans to catch water). This will temporarily restore airflow.
• Visual check of heater: The heater is usually a glass or metal tube at the bottom or woven through the evaporator. Look for breaks, burn marks, or disconnected wires.
• Check defrost thermostat: The thermostat (bi-metal) is clipped to the evaporator tubing. Ensure it is firmly attached and not physically damaged.

Electrical testing of the heater and thermostat requires a multimeter and should be done by a qualified technician. If components test good, the main control board may not be energizing the heater and may need replacement.