E12
Sime
DHW Outlet Over-Temperature / Sensor Disagreement
E12 error on Sime water heater; unit may start but then shut down with temperature-related fault.
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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
Scaled heat exchanger causing hot spots, Faulty DHW outlet NTC, Poor water flow through heater, Miscalibrated control board
How to Fix / Troubleshooting
Safety: Hot water can cause scalding. Allow the unit to cool and close water and gas valves before internal work.
Steps:
- Check flow rate: Ensure hot taps are fully open and aerators are not blocked. Low flow can cause high outlet temperatures.
- Clean inlet filter: Remove and clean the cold water inlet filter to improve flow.
- Inspect DHW NTC: Check the outlet temperature sensor for good contact with the pipe and clean any scale or corrosion.
- Descale: If you have very hard water and the heater is older, arrange for a professional descaling of the primary heat exchanger.
Professional help: Persistent E12 may require sensor replacement or control board calibration by a Sime technician.
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Repair Difficulty
Medium
3/5
Required Part
DHW Outlet NTC Sensor
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