Technical description
Electronics/sensor/analogue-to-digital converter fault
What causes this fault?
This fault occurs when the boiler's main control board fails to correctly interpret the electrical signals coming from its internal sensors. It is usually caused by a critical electronic failure within the circuit board itself or a short circuit in the wiring that confuses the boiler's computer. In some cases, a faulty temperature sensor can send an erratic voltage that the system can no longer process safely.
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.