A21
Ferroli
Control Board / User Interface Communication Fault
Boiler shows A21; often related to communication or configuration issues between control board and user interface.
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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
Loose harness between PCB and display, Faulty user interface board, Main PCB fault, Incorrect parameter configuration
How to Fix / Troubleshooting
Safety first: Isolate power before removing the front panel or accessing electronics.
- Power reset: Turn off the boiler at the fused spur for 2–3 minutes, then power back on. This can clear transient communication errors.
- Check for moisture: Ensure there are no signs of water ingress on the front panel or around the boiler that could affect electronics.
- Engineer checks:
- Inspect and reseat the low-voltage harness between the main PCB and display.
- Check for damaged tracks or components on the user interface board.
- Replace the user interface or main PCB if communication cannot be restored.
- Verify and reprogram boiler parameters if corrupted.
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Repair Difficulty
Hard
4/5
Required Part
Main PCB (Control Board)
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