F2
Saunier Duval
Room Temperature Sensor Short Circuit
Thermostat shows F2 and indicates an abnormally high room temperature or no temperature reading
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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
Shorted NTC sensor inside thermostat, Moisture or condensation bridging sensor pins, Solder bridge or debris on PCB, Incorrect wiring causing external voltage on sensor circuit
How to Fix / Troubleshooting
Safety: Turn off power to the boiler and thermostat before opening any covers.
- Check environment: If the thermostat is installed in a bathroom, kitchen, or other humid area, remove it from the wall and inspect for condensation. Allow it to dry thoroughly.
- Inspect for contamination: Look for dust, insects, or metallic debris inside the thermostat vents that could short the sensor area. Gently clean with a soft brush and compressed air (no liquids).
- Verify wiring: Ensure no external wires are connected to terminals intended only for low‑voltage bus (eBus/OTBus). Incorrect 230 V connection can damage the sensor circuit.
- Reset: Perform a factory reset and re-pair with the boiler if required.
If F2 persists, the internal sensor or PCB is damaged and the thermostat should be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Saunier Duval Smart Thermostat Main PCB / Sensor Circuit
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