E05
EHC
Return Temperature Sensor Fault
Boiler shows E05, may run briefly then shut down, often related to return temperature readings.
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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, Loose or corroded sensor connector, Damaged harness between sensor and PCB, PCB fault
How to Fix / Troubleshooting
Safety: Turn off the boiler at the isolator before removing covers.
Engineer checks:
- Identify the return NTC sensor on the return pipe entering the EHC boiler.
- Measure sensor resistance and compare with the manufacturer’s NTC curve.
- Inspect wiring and connectors for signs of overheating, moisture ingress or mechanical damage.
- Check for correct seating of the sensor in its pocket and good thermal contact (use thermal paste if specified).
- If sensor and wiring are correct, test PCB by substitution or manufacturer diagnostics.
Replace the return NTC sensor if it is out of tolerance or intermittently open/short.
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Repair Difficulty
Medium
3/5
Required Part
Return NTC Sensor
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