F6
Certikin
Water Temperature Sensor (NTC) Fault
Heater display shows F6 and will not respond to a call for heat.
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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
Open-circuit or shorted NTC sensor, Damaged sensor cable, Poor connection at control PCB sensor terminals, Incorrectly positioned sensor in Certikin flow manifold
How to Fix / Troubleshooting
Safety first: Isolate electrical power before removing panels or touching wiring.
- Locate the NTC sensor: On most Certikin pool heaters, the water temperature sensor is mounted in the flow manifold or on a pocket in the heat exchanger outlet.
- Check wiring: Inspect the sensor cable for cuts, abrasions, or rodent damage. Ensure the plug or terminal block at the control PCB is firmly seated.
- Sensor seating: Confirm the sensor is fully inserted into its pocket or well and secured with the retaining clip or compression fitting.
- Visual corrosion check: Look for corrosion on the sensor terminals and clean gently if needed.
- Reset and test: Restore power and see if the F6 code clears. If it returns immediately, the sensor is likely defective.
Replacement of the NTC sensor is usually straightforward but must be done with the system depressurised and isolated. If in doubt, contact a technician.
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Repair Difficulty
Medium
3/5
Required Part
Certikin water temperature sensor (NTC)
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