F9
Saunier Duval
Return temperature sensor / secondary NTC fault
F9 displayed, unit may overheat or shut down unexpectedly
Advertisements
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.
Advertisements
Possible Causes
Defective return NTC sensor, Wiring harness damage, Poor thermal contact between NTC and pipe, Faulty PCB sensor input
How to Fix / Troubleshooting
Safety first: Isolate power and allow the appliance to cool.
Steps:
- Locate return NTC: On combination models or heaters with recirculation, the return NTC is on the return pipe to the heat exchanger.
- Check mounting: Ensure the sensor is firmly clipped and has good contact with the pipe. Refit with thermal paste if specified by Saunier Duval.
- Inspect wiring: Follow the cable back to the PCB, checking for damage or loose plugs.
- Replace sensor: Swap the return NTC with a known-good part. If the error remains, the PCB may be at fault.
Warning: Incorrect sensor readings can cause overheating. Do not bypass sensors.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
Return NTC Sensor
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements