Saunier Duval
Unstable outlet temperature
Water heater works but hot water temperature fluctuates significantly during a shower
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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
Flow sensor signal unstable, NTC sensor loose or poorly positioned, Rapid changes in inlet water temperature, Oversized heater cycling at low demand
How to Fix / Troubleshooting
Safety first: Turn off power before accessing sensors or flow components.
Steps:
- Stabilize flow: Avoid opening and closing other taps while showering. Keep a steady flow rate.
- Clean flow sensor: Remove and clean the Saunier Duval flow sensor turbine to ensure smooth rotation.
- Check NTC mounting: Ensure DHW and primary NTC sensors are firmly clipped to pipes or in their pockets with good thermal contact.
- Descale: If scaling is suspected, have the heat exchanger descaled to improve control response.
Warning: Temperature swings can cause scalding, especially for vulnerable users. Address promptly.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor
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