E12
Alpha
Flow Sensor / Turbine Error
Display shows E12; water temperature fluctuates and unit may short-cycle.
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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
Stuck flow turbine, Scaled or debris-clogged flow sensor, Faulty flow sensor wiring, Defective flow sensor assembly
How to Fix / Troubleshooting
Safety: Turn OFF power and close the cold water supply to the heater. Relieve pressure by opening a hot water tap.
- Locate flow sensor: On Alpha tankless models, the flow sensor is typically on the cold water inlet manifold.
- Remove and inspect: Carefully remove the flow sensor assembly. Check the internal turbine wheel for mineral buildup or debris. It should spin freely.
- Clean: Soak the sensor in white vinegar or a manufacturer-approved descaler to dissolve scale. Rinse thoroughly with clean water.
- Reinstall and test: Refit the sensor, restore water and power, and run hot water. If E12 persists, the sensor or wiring may need replacement.
Use only OEM Alpha flow sensor assemblies to ensure proper calibration.
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Repair Difficulty
Medium
3/5
Required Part
Flow Sensor Assembly
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