BoilerFaultCodesGlow-worm F11 Fault Code
The Glow-worm F11 fault code means: your boiler's main control board and the display panel are having trouble talking to each other, which has caused the system to stop working.. It appears on 12 Glow-worm models in our database.
Technical description: User interface / Main PCB communication fault
What causes the Glow-worm F11 fault?
This fault occurs when the data connection between the boiler's main brain and the control panel on the front of the unit is broken. The most common cause is a loose internal wire or moisture damage affecting the delicate circuit boards, preventing them from sending signals to each other. Because the control panel can no longer 'talk' to the engine of the boiler, the system shuts down as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Glow-worm models that show the F11 fault code
Click a model for the full fault code list and model-specific repair notes.
- 30ci Plus Repair: £280-£450
- Ci Plus Repair: £180-£450
- Flexicom 18sx Repair: £90-160
- Flexicom hx Repair: £90-160
- Flexicom sx Repair: £90-160
- Ultracom 2 CXI Repair: £100-£180
- Ultracom 2 HXI Repair: £100-£180
- Ultracom 24cx 30cx Repair: £100-£180
- Ultracom 35 Store Repair: £100-£180
- Ultracom cxi Repair: £100-£180
- Ultracom hxi Repair: £100-£180
- Xtramax HE Repair: £250-£450
Source
Glow-worm F11 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