E05
Main
Flow Temperature Sensor (NTC) Fault
Boiler shows E05, heating and hot water unavailable, temperature reading may be erratic
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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 or short-circuit flow NTC sensor, Loose sensor wiring, Corroded connector on main PCB, Limescale build-up affecting sensor pocket
How to Fix / Troubleshooting
Safety: Isolate electrical power before removing the boiler front cover. Allow the boiler to cool.
- Reset and observe: Reset the boiler and watch the displayed temperature. If it jumps rapidly or shows unrealistic values, the NTC is likely faulty.
- Inspect wiring: With power off, visually inspect the wiring harness from the flow NTC sensor on the Main primary heat exchanger to the PCB for damage or loose plugs.
- Check sensor connection: Ensure the NTC is firmly seated in its pocket and the retaining clip is secure.
- Engineer checks:
- Measure the resistance of the flow NTC at a known temperature and compare with Main’s resistance chart.
- Inspect for scale or sludge around the sensor pocket that could cause overheating or poor thermal contact.
- Test the PCB sensor input circuit; replace the Main control PCB if the sensor tests good but fault persists.
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Repair Difficulty
Medium
3/5
Required Part
Flow NTC Sensor
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