Your boiler has detected that it is getting dangerously hot and has shut itself down to prevent damage or a safety hazard.

Temperature fault (safety circuit): Flue or high limit thermostat activated ▶ Check: – Flue & high limit thermostat harness and connector. – Operation, replace if necessary. – Circulation within heating system. – Burner gasket for leakage of flue gasses, replace if necessary. – Heat exchanger for debris. – Air-gas ratio.