E3
Remeha
Return temperature sensor (NTC) fault
Boiler shows E3 and locks out
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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
Defective return NTC sensor, Loose or corroded NTC connector, Damaged sensor cable, Faulty main control PCB
How to Fix / Troubleshooting
Safety first: Turn off power before removing the boiler front panel.
- Reset and observe: Reset the boiler and see if E3 returns immediately or only when hot. This helps an engineer diagnose intermittent sensor faults.
- Inspect return NTC: The return NTC is usually clipped to the return pipe entering the boiler. Check that it is firmly attached and that the wiring plug is fully seated.
- Check for water leaks: Look for any signs of water ingress around the sensor or wiring that could cause corrosion or shorting.
- Engineer tasks: A professional should test the resistance of the return NTC, compare with the flow NTC, and replace the sensor or harness if readings are incorrect. If sensors are fine, the PCB input may be defective.
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Repair Difficulty
Hard
4/5
Required Part
Return Temperature Sensor (NTC)
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