F70 High

Glow-worm F70 Fault Code

The Glow-worm F70 fault code means: your boiler's main control board has lost communication with its internal identity chip, effectively meaning the boiler has forgotten which model it is and cannot operate.. It appears on 17 Glow-worm models in our database.

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: PCB personality chip fault

What causes the Glow-worm F70 fault?

This fault occurs when the boiler's main control board loses its connection to the identity chip that tells it how to operate correctly. The most common reason is a hardware failure within the printed circuit board (PCB) or a loose connection to the data chip, often caused by age or electrical wear. In some cases, this can also happen after a replacement part has been installed but not correctly coded to the specific boiler model.

Typical repair cost £250-450 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Glow-worm models that show the F70 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Glow-worm F70 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026