Boiler starts then shuts down after a few seconds, with no specific error code, radiators and hot water remain cold.

Safety: Allow the boiler to cool between repeated start attempts to avoid overheating.

• Bleed air: Bleed radiators and any air vents near the boiler to remove trapped air.
• Check pump: Confirm that the pump is running when the boiler fires. If not, the boiler may quickly overheat and shut down.
• Observe temperature rise: If the temperature on the display shoots up rapidly then the boiler stops, there is likely a flow restriction.
• Engineer service: A technician should check NTC sensors, clean or replace the primary heat exchanger, and verify pump performance.