BoilerFaultCodesTechnical description
Different temperature error
What causes this fault?
This fault occurs when the boiler's internal sensors detect a drastic temperature difference that shouldn't be there, suggesting the heat isn't being moved away from the burner correctly. The most common reason is a pump failure or a blockage in the pipework preventing water from circulating, though it can also be triggered by a sensor that has started providing inaccurate readings. Because the boiler cannot safely verify the actual water temperature, it shuts down to prevent overheating.
This issue is more common in autumn when heating systems are turned back on after a long summer break, as circulation pumps can seize or sludge can settle during 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.