E12
EHC
Flow Sensor / Turbine Fault (DHW Flow Detection)
Boiler intermittently locks out with E12, especially during hot water use, with fluctuating temperatures.
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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
Sticking DHW flow turbine, Blocked flow sensor by debris, Faulty Hall sensor on flow meter, Wiring fault to PCB
How to Fix / Troubleshooting
Safety: Isolate power and water before removing any DHW components.
User checks:
- Clean inlet filters on taps and shower heads to improve flow.
- Ensure stopcocks and service valves on the cold inlet to the boiler are fully open.
Engineer checks:
- Remove and inspect the DHW flow sensor/turbine assembly on the EHC combi boiler cold inlet.
- Clean any debris or scale from the turbine and housing; ensure the turbine spins freely.
- Test the Hall sensor output with a multimeter while water flows; replace the sensor or complete flow meter if no pulses are detected.
- Check wiring continuity from the flow sensor to the PCB.
After cleaning or replacing the flow sensor, run several hot water tests to confirm stable operation.
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Repair Difficulty
Hard
4/5
Required Part
DHW Flow Sensor / Turbine Assembly
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