High Lockout
F70 on Glow-worm Flexicom hx

Your boiler's internal control boards are not communicating correctly because they do not recognise each other's software or settings.

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

Display and Main PCB incompatible

What causes this fault?

This fault occurs when the boiler's two internal computer brains—the main circuit board and the display board—lose their digital connection or fail to recognise each other. The most common reason is that one of the boards has been replaced with an incorrect version, or a sudden electrical surge has corrupted the software settings that link them together.

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

F61View →F62View →F63View →

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