High Lockout
A05 on Potterton Powermax HE

Your boiler's electronic brain has detected an internal safety error and has shut down for protection.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Safety relay failure (in boiler control). Switch OFF/ON - press RESET. Replace boiler control Part No. 5107535

What causes this fault?

This fault occurs when the boiler's internal safety checks detect a failure in the electronic components that manage gas flow and ignition. Essentially, a critical safety switch inside the control board has become stuck or damaged, preventing the boiler from firing up safely. Because the system can no longer verify that it is safe to operate, it shuts down to prevent any potential hazards.

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.

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Related fault codes

A01View →E01View →

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