Boiler displays F6 and stops heating, temperature readings appear incorrect
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off electrical power and close the gas valve. Allow the boiler to cool.
Steps to check DHW NTC:
- Locate the DHW NTC sensor on or near the domestic hot water plate heat exchanger (usually on the cold inlet or hot outlet side).
- Inspect the sensor body and mounting clip. Ensure it is firmly in contact with the pipe or inserted fully into its pocket.
- Disconnect the sensor and measure its resistance at room temperature. Compare with the Protherm NTC chart. Replace the sensor if readings are out of tolerance, open, or shorted.
- Check the wiring harness from the sensor to the PCB for continuity and signs of damage. Repair or replace as needed.
- If the sensor and wiring are OK, the PCB may be faulty. Replacement should be done by a qualified technician.
After repair: Reassemble, restore power and gas, reset the boiler, and run a hot water tap to confirm stable temperature and that F6 has cleared.
Repair Difficulty
Required Part
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