How much does it cost to fix Glow-worm error code d.34?

Typical repair cost for the Glow-worm d.34 fault is £180-350 including labour.

d.34 High

Glow-worm d.34 Fault Code

Q: What does the Glow-worm d.34 fault code mean?

Your boiler has detected that the internal fan responsible for venting exhaust gases is not spinning at the correct speed, so it has shut down to keep you safe.

Also written as D34 — same fault.

The Glow-worm d.34 fault code means: your boiler has detected that the internal fan responsible for venting exhaust gases is not spinning at the correct speed, so it has shut down to keep you safe.. It appears on 11 Glow-worm models in our database.

Technical description: Speed of fan

Typical repair cost £180-350 (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 d.34 fault code

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

Source

Glow-worm d.34 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