Boiler shows E07, external sensor fault (e.g., outdoor sensor)

Safety: Isolate power before working on sensor wiring.

Steps:

• Inspect sensor: Locate the outdoor sensor on the north or shaded wall. Check that it is intact and not filled with water.
• Check cable: Follow the cable back to the boiler, looking for cuts or crushed sections. Reseat the terminals.
• Compare temperature: If the displayed outdoor temperature is unrealistic, the sensor is likely faulty.

Professional help: Replace the sensor with the correct De Dietrich part and verify weather compensation settings.