Technical description
Burner blocked. Short circuit - boiler water temperature sensor.
What causes this fault?
This fault occurs when the boiler's internal thermometer, which monitors how hot the water is getting, fails to send a correct electrical signal to the main control board. The most common reason is that the sensor has suffered an internal electrical short circuit or the connecting wires have become damaged or loose. Because the boiler no longer knows the exact temperature of the water inside, it shuts down the burner as a primary safety precaution to prevent overheating.
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.