Freezer shows F3 and may over-freeze or fail to maintain set temperature

Safety first: Disconnect power. Be cautious of sharp evaporator fins when working inside the freezer.

• Access evaporator area: Remove shelves and the rear inner panel of the freezer to expose the evaporator coil and defrost components.
• Locate defrost sensor: The defrost/evaporator thermistor is usually clipped to the evaporator tubing or attached with a metal clip or tie-wrap.
• Check mounting: Ensure the sensor is firmly attached to the coil. A loose sensor can cause incorrect readings and trigger F3.
• Test sensor: Disconnect the thermistor and measure resistance at freezer temperature (e.g., -18°C). Compare to Hitachi specifications. Infinite or zero resistance indicates a bad sensor.
• Inspect wiring: Look for ice damage, chafed insulation, or corroded connectors in the evaporator compartment. Repair or replace damaged sections.
• Replace sensor: Install a new Hitachi evaporator/defrost thermistor and secure it tightly to the coil in the original position.
• Control PCB: If the sensor and wiring are good, replace the main control PCB as the next step.