Freezer shows F5 and may not cool or may cycle erratically

Safety first: Unplug the freezer. The compressor and surrounding components can be hot; allow them to cool before touching.

• Locate compressor sensor: At the rear of the freezer, find the compressor. The discharge temperature sensor is often clipped or strapped to the compressor shell or discharge line.
• Check attachment: Ensure the sensor is firmly attached and making good thermal contact with the compressor surface.
• Inspect wiring: Look for brittle insulation, cuts, or loose connectors between the sensor and the main control PCB.
• Test sensor: Disconnect the sensor and measure resistance at room temperature. Compare to Hitachi specifications. Replace if reading is open, shorted, or far out of range.
• Replace sensor: Install a new Hitachi compressor temperature sensor and secure it with the original clip or strap.
• Control PCB: If a known-good sensor does not clear F5, the main control PCB may be misreading the sensor and should be replaced.