Freezer displays AL07; the defrost cycle does not run correctly, and frost accumulates on the evaporator.

Safety first: Unplug the freezer. Do not chip ice with sharp tools, as you can puncture refrigerant lines.

Procedure:

• Inspect frost pattern: Remove the interior rear panel to view the evaporator. A solid block of ice indicates a defrost failure.
• Locate defrost thermostat/thermal fuse: It is usually clipped to the evaporator tubing and wired in series with the defrost heater.
• Test continuity: With the evaporator still cold, disconnect the thermostat/fuse and check continuity with a multimeter. An open reading on a cold coil indicates a failed thermostat or fuse, which must be replaced.
• Check defrost sensor (if separate NTC): Measure resistance and compare it to the specifications. Replace if out of range.
• Inspect connectors: Ensure all plugs in the defrost circuit (heater, thermostat, sensor) are firmly seated and free of corrosion.
• If all components test OK: The main control board may not be initiating defrost. Replace the control module after verifying the supply voltage and wiring.