Freezer displays E04 and may show abnormal temperature swings or continuous alarm beeping.

Safety: Unplug the appliance before opening the control housing.

Steps:

• Locate ambient sensor: On many Bosch freezers, the ambient NTC is located near the control panel or in the top/front housing where air from the room can reach it.
• Visual inspection: Remove the control panel cover (usually clipped or screwed). Look for a small sensor probe or plastic capsule with two wires.
• Check wiring and connector: Ensure the sensor connector is fully seated on the control board. Look for corrosion or moisture damage.
• Test sensor: Disconnect the sensor and measure resistance at room temperature. Compare to Bosch NTC chart if available. If reading is open or shorted, replace the sensor.
• Replace sensor: Install a new Bosch-compatible ambient NTC, routing wires away from sharp edges and securing them with clips or tape.
• Control board evaluation: If the sensor tests good and E04 persists, the control board may misread the sensor. Replacement of the main control module may be required.

Tip: Ensure the freezer is not installed in an environment outside the specified ambient temperature range, as extreme conditions can also trigger sensor-related alarms.