A12
Fondital
DHW Flow Detection Fault
Boiler shows A12, no domestic hot water even though heating works correctly
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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
Stuck DHW flow switch or turbine on Fondital hydraulic group, Blocked DHW inlet filter, Limescale in DHW flow sensor, Faulty DHW microswitch or Hall sensor
How to Fix / Troubleshooting
Safety: Turn off power and close the cold water inlet valve before any work on water connections.
User checks:
- Check other taps: Confirm cold water supply is present and pressure is normal.
- Clean tap aerators: Remove and clean aerators on hot taps to ensure good flow.
- Reset: Reset the boiler once. If A12 persists, internal DHW components need inspection.
Technician actions:
- Inspect and clean the DHW inlet filter on the Fondital boiler.
- Disassemble and clean or replace the DHW flow sensor / turbine or flow switch.
- Test the DHW microswitch or Hall sensor and wiring to the PCB.
- Check for limescale in the DHW plate heat exchanger and descale if necessary.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor
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