E3
Worcester
Return Temperature Sensor (NTC) Fault
Boiler shows E3, may run briefly then shut down, often related to return temperature sensing.
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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
Failed Worcester return NTC sensor, wiring harness damage, poor connector contact at sensor or PCB, control board fault
How to Fix / Troubleshooting
Safety first: Turn off power before any internal inspection.
Homeowner actions:
- Reset the boiler once and observe. If E3 reappears, further diagnosis is needed.
- Ensure system pressure is correct and radiators are bled, although the root cause is usually electrical.
Engineer actions:
- Test the resistance of the Worcester return NTC and compare with specification.
- Inspect wiring from the NTC to the PCB for damage or signs of overheating.
- Clean and reseat connectors to ensure good contact.
- Substitute a known-good NTC to confirm diagnosis before replacing the PCB.
Sensor replacement is a common fix; PCB replacement should only follow proper testing.
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Repair Difficulty
Hard
4/5
Required Part
Return Temperature Sensor (NTC)
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