E12
State
Control Board Internal Error
State tankless water heater shows E12; unit may operate intermittently or lock 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
Failed control PCB, Power surge damage, Corroded board connectors
How to Fix / Troubleshooting
Safety: Disconnect power before opening the control compartment.
- Inspect board: Remove the front cover and locate the main control board. Look for burn marks, swollen components, or moisture damage.
- Check connectors: Reseat all harness connectors to the board. Ensure no pins are bent.
- Power quality: Verify the heater is on a dedicated circuit with proper grounding. Consider adding surge protection.
- Replace board: If E12 persists after reseating connectors and verifying supply voltage, replace the control board with the correct State replacement part. This is typically a technician-level repair.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board (PCB)
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