A11
Fondital
Insufficient Water Circulation / Air in System
Boiler displays A11, burner stops, sometimes accompanied by gurgling noises in the boiler
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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
Air trapped in primary heat exchanger, Blocked automatic air vent on Fondital boiler, Partially blocked primary circuit, Weak circulation pump
How to Fix / Troubleshooting
Safety: Allow the boiler to cool. Hot water and surfaces can cause burns.
User checks:
- Bleed radiators: Remove air from all radiators and towel rails.
- Check pressure: Maintain system pressure at 1.0–1.5 bar cold after bleeding.
- Listen for noises: Gurgling or trickling sounds indicate air; continue bleeding until reduced.
Technician actions:
- Check and replace the automatic air vent on the boiler if it is blocked or leaking.
- Verify correct operation of the circulation pump and speed settings.
- Flush the primary circuit and primary heat exchanger if sludge is present.
- Check for partial blockages in the hydraulic manifold.
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Repair Difficulty
Medium
3/5
Required Part
Automatic Air Vent
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