E12
Hager Internal CAN / UART Communication Fault Between Boards

Hager EV charger displays E12; app may show ‘internal communication error’ or ‘CPU/board communication 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

Loose internal harness between main control board and communication board, Faulty daughterboard (e.g. Wi‑Fi/4G module), Firmware mismatch between boards, Main control board failure

How to Fix / Troubleshooting

Safety first: Isolate power at the upstream breaker before any disassembly. Only qualified personnel should open the enclosure.

Steps to try:

  • Power-cycle: Turn OFF the charger’s breaker for 2 minutes, then turn it back ON. Many transient internal comms faults clear after a full reboot.
  • Check for firmware updates: Using the Hager app or web interface, check for and apply any available firmware updates, following Hager’s instructions.
  • Technician inspection: If E12 persists, a technician should open the unit, reseat internal connectors between the main board and any communication or metering boards, and inspect for damage.
  • Replace faulty board: If communication cannot be restored, replace the affected daughterboard or the main control board according to Hager service documentation.
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Repair Difficulty

Hard 4/5

Required Part

Internal Communication Harness / Daughterboard
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