E05
Alpha
Return Temperature Sensor (NTC) Fault
Boiler shows E05, runs briefly then shuts down, often associated with incorrect 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
Open-circuit return NTC sensor, Shorted return NTC sensor, Loose NTC connector, Damaged wiring harness
How to Fix / Troubleshooting
Safety: Switch off the boiler at the mains before removing any covers.
- Visual inspection: Locate the return NTC sensor on the return pipe entering the boiler. Check that the sensor clip is secure and the cable is intact.
- Connector check: Ensure the NTC plug is fully seated on the main PCB or intermediate connector block.
- Moisture check: Look for any signs of water leaks around the return pipe that could have dripped onto the sensor or wiring. Fix leaks before replacing components.
- Test sensor (qualified person): Disconnect the sensor and measure its resistance. Compare with Alpha's specified values at room temperature. Replace the sensor if readings are out of range.
Persistent E05 after sensor replacement suggests a PCB fault and requires professional diagnosis.
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Repair Difficulty
Medium
3/5
Required Part
Return Temperature Sensor (NTC)
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