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 14 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.
Find a Gas Safe engineer
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A cover plan would handle faults like F13: no call-out fees, no surprise bills.
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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.
- CXi Repair: £250-450
- Flexicom 18sx Repair: £90-180
- Flexicom 24c / 28c Repair: £120-220
- Flexicom cx Repair: £200-350
- Flexicom hx Repair: £90-180
- Flexicom hxi Repair: £120-250
- Flexicom sx Repair: £90-180
- Ultracom 2 CXI Repair: £90-160
- Ultracom 2 HXI Repair: £90-160
- Ultracom 24cx 30cx Repair: £90-160
- Ultracom 35 Store Repair: £90-160
- Ultracom cxi Repair: £90-160
- Ultracom sxi Repair: £180-350
- Xtramax HE Repair: £250-£450
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 CXi manual (PDF)
- Glow-worm Flexicom sx manual (PDF)
- Glow-worm Flexicom 24c / 28c manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026