Boiler shows E05, will not start heating; may occur immediately on power-up or when a heating demand is present.

Safety: Isolate power before removing the front cover or touching internal wiring.

• Reset the boiler: Perform a standard reset. If E05 reappears immediately, the sensor or wiring is likely faulty.
• Check sensor connection: With power off, locate the flow NTC sensor on the flow pipe leaving the primary heat exchanger (refer to Atlantic schematic). Ensure the plug is firmly seated and wires are not damaged or corroded.
• Inspect for water ingress: Look for signs of leaks dripping onto the sensor or wiring, which can cause corrosion and false readings.
• Professional testing: A technician can measure the resistance of the NTC at known temperatures and compare to Atlantic specifications, and replace the sensor if out of range.