A20
Fondital
Communication Fault (Bus Error)
Boiler shows A20, display may indicate communication error with remote control or zone module
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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 or reversed polarity on Fondital BUS wiring, Faulty remote control or zone module, Too many devices on BUS without proper configuration, Main PCB communication port fault
How to Fix / Troubleshooting
Safety: Isolate power before working on control wiring.
User checks:
- Remote control: Check that the Fondital remote control or room unit is powered and correctly connected (if plug-in type).
- Cables: Look for obvious damage to visible low-voltage cables.
- Reset: Power the boiler off for 30 seconds and back on to reset communication.
Technician actions:
- Verify correct polarity and continuity of the Fondital BUS wiring.
- Disconnect additional BUS devices and test with a single remote control.
- Replace a faulty remote control / zone module if identified.
- Test the main PCB BUS interface and replace PCB if necessary.
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Repair Difficulty
Medium
3/5
Required Part
Fondital Remote Control (BUS)
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