A9
Nibe
Heating flow temperature sensor fault
A9 alarm, flow temperature reading incorrect, unit cycles or shuts down
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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
Defective flow sensor, poor contact with pipe, wiring fault, sensor not insulated
How to Fix / Troubleshooting
Safety: Isolate power and allow pipes to cool before handling.
- Locate the flow sensor: On Nibe furnaces, the flow sensor is usually clipped or strapped to the heating flow pipe inside the unit. Ensure it is firmly attached and in good thermal contact.
- Insulate the sensor: If the sensor is exposed, wrap it and the pipe with insulation to prevent false readings from ambient air.
- Check wiring: Inspect the cable from the sensor to the control board for damage or loose connectors. Reseat the plug.
- Reset alarm: Restore power and clear the A9 alarm. If the reading is still erratic, replace the sensor.
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Repair Difficulty
Medium
3/5
Required Part
Flow Temperature Sensor
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