F7
Certikin
Return Temperature Sensor / Differential Fault
Display shows F7; heater may run erratically or not at all.
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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
Faulty return NTC sensor, Poor contact between sensor and pipe, Wiring fault between sensor and Certikin control board, Excessive temperature differential due to low flow
How to Fix / Troubleshooting
Safety first: Isolate electrical power before working on sensors or wiring.
- Check flow first: Ensure adequate water flow through the heater by verifying pump operation, valve positions, and filter cleanliness.
- Locate return sensor: Identify the return (outlet) temperature sensor on the heater pipework or manifold.
- Inspect mounting: Make sure the sensor is firmly clamped to the pipe or fully inserted into its pocket, with thermal paste if specified by Certikin.
- Check cable and connections: Look for damage to the cable and ensure the connector at the control PCB is secure.
- Reset and monitor: Restore power and observe operation. If F7 reappears, the sensor or PCB may be faulty.
Accurate diagnosis may require resistance measurements of the NTC sensor against Certikin specifications; this is best done by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Certikin return temperature sensor (NTC)
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