BoilerFaultCodesGlow-worm F13 Fault Code
The Glow-worm F13 fault code means: your boiler's main control board has encountered an internal electronic error, meaning the 'brain' of the system can no longer manage the heating and hot water safely.. It appears on 6 Glow-worm models in our database.
Technical description: Main PCB fault.
What causes the Glow-worm F13 fault?
This fault occurs when the boiler's internal computer experiences a critical electronic failure or a 'brain freeze' that prevents it from processing commands. It is typically caused by a short circuit on the control board, aged components failing over time, or a communication error between the board and the wiring harness.
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 F13 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Glow-worm F13 fault code information on this page is sourced and cross-checked against the official Glow-worm service / installation manuals for each affected model.
- Glow-worm Flexicom 18sx manual (PDF)
- Glow-worm Flexicom 30sx manual (PDF)
- Glow-worm Ultracom 35 Store manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026