F42
Ferroli Temperature Sensor Correlation Fault

Boiler displays F42; may be associated with temperature sensor plausibility or differential issues.

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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 and return NTC readings inconsistent, Airlock or no circulation, Faulty NTC sensor, PCB calculation fault

How to Fix / Troubleshooting

Safety first: Turn off power and allow boiler to cool before working on it.

  • Check system pressure and bleed: Ensure adequate pressure and remove air from radiators and high points.
  • Engineer checks:
    • Compare flow and return NTC readings at the same temperature.
    • Replace any NTC sensor with incorrect readings.
    • Verify pump operation and system circulation.
    • Replace PCB if sensor readings are correct but F42 persists.
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Repair Difficulty

Hard 4/5

Required Part

Flow and Return NTC Sensors
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