Display shows E3 and the compressor may run continuously or not at all; temperature reading on display is clearly wrong.

Safety first: Disconnect the appliance from mains before opening the control panel. Avoid static discharge when handling electronic boards.

Step-by-step checks:

• 1. Confirm symptom: Compare the displayed ambient or cabinet temperature with an accurate thermometer. If the reading is unrealistic (e.g., -20°C when room is 25°C), suspect the ambient sensor.
• 2. Access control panel: Remove the screws or clips holding the top/front control panel. Carefully pull it forward to expose the display PCB and sensor wiring.
• 3. Locate ambient sensor: On many Hansa models, the ambient sensor is a small NTC embedded near the control panel vents or in the top frame. Identify the two-wire harness labeled for ambient or room sensor.
• 4. Inspect and reseat: Check for loose plugs, corrosion, or moisture around the connector. Dry any condensation and reseat the connector firmly.
• 5. Measure resistance: With the freezer unplugged, disconnect the sensor and measure its resistance at room temperature. If it reads open, shorted, or far outside the expected range, replace the sensor.
• 6. Evaluate the PCB: If the sensor tests good, inspect the display/control PCB for damage. If no visible damage but E3 persists, the PCB may need replacement.

Tip: Label all connectors before removal to avoid miswiring when reassembling.