Refrigerator or freezer displays EC24; unit may not defrost properly, with ice buildup on evaporator and warm temperatures.

Safety first: Disconnect power before accessing any internal components. Melted plastic and live wiring are hazards; do not use sharp tools to remove ice.

Step 1 – Confirm symptoms

• Check for heavy frost or solid ice buildup on the evaporator cover or back wall of the refrigerator/freezer section.
• Listen for the evaporator fan; if it is hitting ice or is blocked, you likely have a defrost issue.

Step 2 – Manual defrost to restore temporary cooling

• Remove all food from the affected compartment and store in a cooler.
• Leave doors open and unplug the unit for 12–24 hours to allow all ice on the evaporator to melt. Place towels to catch water.
• This may restore cooling for a short period but does not fix the underlying fault.

Step 3 – Access the evaporator and defrost components

• With power off, remove shelves and the evaporator cover panel in the affected section.
• Locate the defrost heater (usually at the base or woven through the evaporator) and the defrost bi‑metal/thermostat clipped to the evaporator tubing.

Step 4 – Test defrost heater and bi‑metal

• Disconnect heater leads and measure resistance with a multimeter. A typical Sub‑Zero defrost heater should show continuity (not open). An open reading indicates a failed heater.
• Test the defrost bi‑metal for continuity when it is cold (you can place it in ice water). It should read closed (low resistance) when cold. If it remains open, replace the bi‑metal.

Step 5 – Inspect wiring and control

• Check connectors and harnesses for corrosion or loose pins between the evaporator area and the main control board.
• If heater and bi‑metal test good, the issue may be with the main control board or defrost relay, which typically requires professional diagnosis and replacement.

When to call a professional: If you are not comfortable using a multimeter, or if both heater and bi‑metal test good but EC24 persists, contact a Sub‑Zero authorized technician. They can access diagnostic mode, verify defrost timing, and replace the control board if needed.