BoilerFaultCodesTechnical description
The display shows alternatively the CH flow temperature and E9. The gradient limitation is active. The primary temperature is rising too fast and the burner has switched off for 2 minutes. See error E9.
What causes this fault?
This fault occurs when the water inside the boiler heats up at an abnormally fast rate, suggesting that the heat isn't being moved away from the burner quickly enough. The most common reasons are a failing pump that cannot circulate the water or a physical blockage, such as limescale or sludge, trapped within the main heat exchanger.
This fault often appears in autumn when the heating is turned back on for the first time, as pumps can seize up after being idle during the summer months.
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.