BoilerFaultCodesPotterton E42 Fault Code
The Potterton E42 fault code means: your boiler's computer brain has encountered a serious internal error and can no longer control the heating or hot water safely.. It appears on 2 Potterton models in our database.
Technical description: Internal control error. Switch OFF/ON at mains isolator. Replace boiler control Part No. 5107535
What causes the Potterton E42 fault?
This fault occurs when the boiler's main electronic circuit board suffers a critical internal failure, meaning it can no longer process data or manage safety checks correctly. It is usually caused by the natural degradation of electrical components over time or a sudden power surge that damages the board's memory.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Potterton models that show the E42 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Potterton E42 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 7 July 2026