Refrigerator runs continuously or cycles erratically; display may show E3 and temperatures are inaccurate or unstable.

Safety first: Unplug the refrigerator before removing the control panel or display housing.

Steps:

• 1. Verify installation conditions: Ensure the refrigerator is not installed in extreme temperatures (e.g., unheated garage below 10 °C or above 38 °C). Incorrect ambient conditions can trigger sensor-related issues.
• 2. Access the control panel: On many Siemens models, the ambient sensor is located behind the top front control/display panel. Remove the trim and screws, then gently pull the panel forward.
• 3. Inspect the ambient sensor: Look for a small probe or capsule attached to the panel or nearby housing. Check for broken leads, discoloration, or moisture damage.
• 4. Test resistance: Disconnect the sensor and measure resistance at room temperature (~20–25 °C). Compare to Siemens specifications (commonly 4–15 kΩ). Replace if open, shorted, or far out of range.
• 5. Check connectors and harness: Reseat the sensor connector and the ribbon cable or harness between the UI and main PCB. Look for bent pins or corrosion.
• 6. Reassemble and test: Refit the panel, restore power, and monitor operation. If E3 returns and the sensor/harness are confirmed good, the main control board may be defective.

Tip: Take photos before disconnecting any connectors to ensure correct reassembly.