E12
United Chargers
User Interface / HMI Communication Failure
E12 error; charger display is on but unresponsive or frozen, and charging cannot be started.
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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
Faulty display module, Loose ribbon cable between display and main board, Firmware crash, Power supply instability to HMI board
How to Fix / Troubleshooting
Safety first: Turn off power at the breaker before removing the front cover or display module.
- Power-cycle: Turn the breaker OFF for 2–3 minutes, then ON. Observe whether the display boots normally.
- Inspect display connections: With power OFF, remove the front cover and check the ribbon cable or harness between the display and main control board. Reseat connectors firmly.
- Check for moisture: Look for condensation or water ingress behind the display window, especially on outdoor units. Dry thoroughly if present and improve weather sealing if needed.
- Firmware update: If accessible via app or web, update firmware to the latest version to address potential UI bugs.
If the display remains frozen or blank while the main board appears powered, the display/HMI module may need replacement.
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Repair Difficulty
Medium
3/5
Required Part
Display / HMI Module
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