F.11
Glow-worm
Boiler Status Feedback Fault
Thermostat displays F.11 and cannot detect boiler status
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Broken feedback wire from boiler to thermostat interface, Incorrect connection to boiler status terminals, Faulty boiler PCB status output, Misconfigured control mode (eBus vs on/off)
How to Fix / Troubleshooting
Safety: Isolate mains power to the boiler before accessing its terminal strip or control panel.
Steps:
- Check the control wiring diagram for your specific Glow‑worm boiler and thermostat combination. Ensure the feedback/status wire is connected to the correct low‑voltage terminals.
- Inspect the cable between boiler and thermostat interface for damage or loose terminations.
- In the thermostat installer menu, confirm that the correct boiler type and control protocol (eBus, OpenTherm, or on/off) is selected.
- Restore power and observe whether the thermostat now shows correct boiler status (e.g. burner on, fault, standby).
Remedy:
- If wiring and configuration are correct but F.11 persists, the boiler’s status output or the thermostat interface input may be faulty.
- Have a Glow‑worm service engineer test the boiler PCB and replace either the PCB or the thermostat interface module as required.
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Repair Difficulty
Hard
4/5
Required Part
Glow-worm boiler control PCB or eBus interface
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