E12
Gledhill
Calibration / Sensor Range Error
E12 displayed, hot water temperature overshoots or is too low despite sensor replacement
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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
Incorrect type of NTC sensor fitted, Poor thermal contact between sensor and pocket, Firmware or calibration fault on PCB, Wiring extended with unsuitable cable
How to Fix / Troubleshooting
Safety: Isolate power and allow the unit to cool before handling sensors.
Steps:
- Verify sensor part number: Check that any replacement NTCs are genuine Gledhill parts or exact equivalents with the correct resistance curve.
- Check installation: Ensure the sensor is fully inserted into the pocket and that any thermal paste or sleeve specified by Gledhill is used. Refit insulation over the pocket.
- Inspect wiring modifications: If the sensor cable has been extended, ensure the same type and gauge of cable was used and that joints are soldered or use proper connectors, not twisted wires.
- PCB reset: Power‑cycle the unit. If E12 persists with correct sensors and wiring, the PCB may have an internal calibration fault and require replacement.
Note: Do not mix sensors from different manufacturers without confirming their characteristics match the original specification.
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Repair Difficulty
Medium
3/5
Required Part
Main Control PCB
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