A07
Fondital
Domestic Hot Water (DHW) Overtemperature
Unit displays A07 and stops, often after running for some time at high temperature.
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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
Scaled DHW heat exchanger, Faulty DHW NTC sensor, Sticking gas valve causing overfiring, Low water flow through DHW circuit
How to Fix / Troubleshooting
Safety: Water may be very hot. Allow the unit to cool before working on it.
- Check DHW flow: Open a hot tap fully and verify that flow is strong. If weak, clean faucet aerators and shower heads, and check any inlet filters on the DHW side of the Fondital heater.
- Temperature setting: Ensure the DHW temperature setpoint on the control panel is not set excessively high. Reduce to a moderate value (e.g., 45–50°C).
- Descale DHW heat exchanger: A plate heat exchanger clogged with limescale will cause local overheating. A technician should isolate and flush the DHW heat exchanger with a descaling solution compatible with Fondital components.
- Check DHW NTC sensor: Inspect the sensor wiring and connector. If readings are erratic or out of range, replace the DHW NTC sensor.
- Gas valve modulation: If the burner does not modulate down at low flow, the gas valve or control board may be faulty and require professional diagnosis.
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Repair Difficulty
Hard
4/5
Required Part
DHW Plate Heat Exchanger
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