F.70 High

Glow-worm F.70 Fault Code

Also written as F70 — same fault.

The Glow-worm F.70 fault code means: your boiler’s control computer has lost its identity settings, meaning it no longer knows which specific model it is and has shut down as a safety precaution.. It appears on 6 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: Invalid product code (DSN)

What causes the Glow-worm F.70 fault?

This fault occurs when the boiler's internal memory loses the crucial identification code that tells it how to operate safely. The most common reason is a communication failure between the main control board and the display screen, often caused by a power surge or a failing electronic component.

Typical repair cost £100-£350 (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 F.70 fault code

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

Source

Glow-worm F.70 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 27 April 2026