Thermostat shows E04 and does not display outdoor temperature; weather-compensation functions are disabled

Safety: Turn off boiler and thermostat power before working on sensor wiring.

• Step 1 – Check installation: Locate the Immergas outdoor sensor on the external wall. Ensure it is firmly mounted, not physically damaged, and not directly exposed to rain jets.
• Step 2 – Inspect cable: Follow the sensor cable back to the thermostat or boiler connection. Look for cuts, crushed sections, or loose terminals. Tighten any loose screws.
• Step 3 – Measure resistance: With power off, disconnect the sensor and measure its resistance with a multimeter. Compare to the Immergas NTC curve (e.g., around 10 kΩ at 25 °C, depending on model). If reading is open or near 0 Ω, the sensor is defective.
• Step 4 – Replace sensor: If faulty, install a new genuine Immergas outdoor NTC sensor. Connect to the designated terminals (often marked OT, EXT, or similar) observing polarity if specified.
• Step 5 – Check configuration: In the thermostat or boiler menu, ensure the outdoor sensor function is enabled. Some models allow disabling it, which can also trigger an error.
• Step 6 – Clear error: Restore power and check if E04 disappears and outdoor temperature is displayed correctly.