BoilerFaultCodesTechnical description
Boiler is not working for central heating or hot water and the display shows ‘HHHHH:::::AAAAA ’ (flashing).
What causes this fault?
This fault occurs when the water within the boiler's heat exchanger reaches an unsafe temperature, triggering a safety cutout to prevent damage. The most common reason is a lack of water flow, often caused by a failing pump or a blockage in the pipework that prevents heat from being carried away from the unit. It can also be triggered by a faulty internal sensor that is incorrectly reporting the temperature to the control board.
This fault is more common when the heating is first turned on after summer, as pump components can seize up during long periods of inactivity.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.