BoilerFaultCodesGlow-worm F43 Fault Code
The Glow-worm F43 fault code means: your boiler's main control unit is confused because a specific internal configuration component is missing or has the wrong electrical profile.. It appears on 9 Glow-worm models in our database.
Technical description: Coded resistance fault
What causes the Glow-worm F43 fault?
This fault occurs when the boiler's main control board loses its identity because a small electronic component called a coding chip is loose, damaged, or missing. The chip tells the computer exactly which model of boiler it is controlling, and without this information, the system shuts down for safety. The most common reason is a component failure within the electrical circuit or a loose connection following a recent repair.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Glow-worm models that show the F43 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F43 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