Boiler displays E05, heating does not start, temperature reading may be unrealistic or fixed.
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 first: Turn off power and allow the boiler to cool before touching any pipework or sensors.
User checks:
- Note the displayed temperature; if it shows an impossible value (e.g., - - or over 99°C when cold), E05 likely indicates a sensor fault.
- Reset the boiler once. If E05 returns, a technician should inspect the sensor.
Technician checks:
- Locate the CH flow NTC sensor on the flow pipe leaving the primary heat exchanger.
- Disconnect the sensor and measure its resistance at room temperature; compare with Termet NTC resistance chart.
- Inspect the wiring harness and plug for damage or corrosion; repair or replace as needed.
- If resistance is correct and wiring is sound, test the main PCB sensor input; replace PCB if confirmed faulty.
Replacing a faulty NTC sensor is usually straightforward but must be done with the system depressurised and sealed correctly afterwards.
Repair Difficulty
Required Part
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