d.08 Medium

Glow-worm d.08 Fault Code

Also written as D08 — same fault.

The Glow-worm d.08 fault code means: your boiler is currently receiving a signal from your thermostat that it is time to heat up, but there may be a loose connection or a fault in the communication between your wall controller and the boiler.. It appears on 6 Glow-worm models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Status of the 230V thermostat
Typical repair cost £90-180 (including labour)

DIY fix possible

Check that your external room thermostat is set correctly and the batteries are fresh.Ensure the thermostat wiring at the boiler terminal block is securely connected and not loose.Power cycle the boiler by switching it off at the fused spur for one minute, then turning it back on.

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Glow-worm models that show the d.08 fault code

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

Source

Glow-worm d.08 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 7 July 2026