E12 displayed; freezer may show high temperature alarm even though it feels cold.

Safety: Disconnect power before accessing sensors or control boards.

Steps:

• Verify actual temperature: Place an accurate thermometer in the freezer and compare to the displayed temperature after several hours.
• Inspect sensor location: Ensure the freezer NTC sensor is correctly positioned and not touching the defrost heater or warm surfaces.
• Check for moisture: Look for condensation or water ingress around the sensor housing and wiring. Dry thoroughly if present.
• Test sensor resistance: Measure the NTC resistance at a known temperature and compare to Bosch specifications. Replace the sensor if readings are out of tolerance.
• Confirm correct part: If the sensor was recently replaced, verify that the correct Bosch part number was used. An incorrect NTC curve can cause E12.
• Control module: If sensor and wiring are correct, the main control board may have a calibration fault and require replacement.