High Lockout
A18 on Potterton Powermax HE

Your boiler has stopped working because the internal computer and its sensors are no longer communicating correctly with each other.

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

Control/sensor failure

What causes this 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 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 →A19View →

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