120FF High

Glow-worm 120FF Fault Code

The Glow-worm 120FF fault code means: the code you are seeing refers to the technical heat output rating of your specific boiler model rather than a fault error, though if your boiler has stopped working, it indicates an underlying failure that requires professional diagnosis.. It appears on 1 Glow-worm model 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: NOMINAL kW HEAT INPUT(NETT) Min. 33.43 Medium 36.52 Max. 39.6
Typical repair cost £150-350 (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 120FF fault code

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

Source

Glow-worm 120FF 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