Boiler displays E18; may be associated with external sensor or weather compensation probe.

Safety: Isolate power before working on wiring.

Steps:

• Locate outdoor sensor: Find the Attack external temperature sensor on the outside wall. Check that it is intact and not waterlogged.
• Inspect cable: Follow the cable back to the boiler, looking for cuts or crushed sections.
• Check connections: At the boiler terminal strip, ensure the sensor wires are firmly clamped in the correct terminals.
• Temporary bypass: If allowed by the manual, you may disable weather compensation in the control menu to restore operation until the sensor is replaced.

Technician: If replacing the sensor does not clear E18, the PCB input should be tested by a professional.