Freezer displays E4 and may stop cooling or run continuously; compressor operation is erratic.

Safety warning: Unplug the freezer and allow the compressor area to cool before working. Avoid contact with hot pipes and capacitors.

Diagnostic and repair steps:

• Access compressor compartment: Move the freezer away from the wall. Remove the lower rear metal cover to expose the compressor, condenser, and control board area.
• Locate the discharge/condenser sensor: This thermistor is usually clipped to the compressor discharge line or attached to the condenser tubing. It will have two small wires leading back to the control board.
• Inspect physical condition: Check that the sensor is firmly attached to the pipe and that its insulation is intact. Reattach any loose clips or brackets.
• Test the sensor: Disconnect the sensor from the harness and measure resistance with a multimeter. Compare to expected NTC values. If the reading is open, shorted, or far off spec, replace the sensor with a Sharp-compatible discharge/condenser thermistor.
• Check wiring: Inspect the harness from the sensor to the main PCB for heat damage, melted insulation, or chafing against metal edges. Repair or replace as needed.
• Control board check: If the sensor and wiring are good but E4 persists, the main control PCB may be misreading the sensor. Inspect for visible damage and replace the PCB if necessary.

After repair: Reinstall the rear cover to ensure proper airflow over the condenser. Restore power and monitor compressor operation and error display for several hours.