BoilerFaultCodesPotterton A18 Fault Code
The Potterton A18 fault code means: your boiler has stopped working because the internal computer and its sensors are no longer communicating correctly with each other.. It appears on 1 Potterton model in our database.
Technical description: Control/sensor failure
What causes the Potterton A18 fault?
This fault occurs when the boiler's main control board loses the ability to accurately read data from its internal temperature sensors. It is usually caused by a physical failure within the circuit board itself or damaged wiring that prevents electrical signals from reaching the central processor.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Potterton models that show the A18 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton A18 fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026