Error 31: The unit indicates an external sensor or remote control communication fault (if fitted).

Safety: Disconnect power before working on low‑voltage wiring.

• Check external sensor wiring: For systems using an outdoor sensor or remote controller, verify that the two‑core cable is connected correctly at both the sensor and the Immergas control terminals.
• Inspect cable: Look for damage along the cable route, especially at entry points.
• Bypass test (if allowed): Temporarily disconnect the external sensor to see if the unit reverts to internal control (refer to manual). Do not leave wiring shorted unless specified.

Note: If the external control is defective, replace it with a compatible Immergas accessory.