Boiler shows A08, no heating, return temperature reading abnormal

Safety: Isolate electrical power before accessing internal components.

Steps:

• Locate return sensor: Find the NTC sensor on the return pipe entering the boiler or on the hydraulic block.
• Check mounting: Ensure the sensor is properly clipped to the pipe or inserted in its pocket with thermal paste if specified.
• Inspect wiring: Look for pinched or broken wires between the sensor and the main control board. Reseat the connector.
• Reset and test: Restore power and reset the boiler. If the error persists, the sensor is likely faulty.

Professional help: Replacement of the return NTC is usually simple but should be done with the system depressurised if the sensor is wet‑pocket type.