E04
United Chargers Overvoltage on Supply Line

Charger shows E04 and does not charge; may occur intermittently during sessions.

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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

Utility line voltage above charger rating, Incorrect supply wiring (e.g., 3-phase to single-phase unit), Loose neutral or line connection causing spikes, Faulty internal voltage sensing circuit on control board

How to Fix / Troubleshooting

Safety first: Only a qualified electrician should measure live voltages. Turn off power before opening the charger.

  • Check supply rating: Confirm the charger model’s input voltage rating (e.g., 208–240 V single-phase) and compare with your electrical service.
  • Measure line voltage: Have an electrician measure L1–L2 (and L–N if applicable) at the charger terminals under load. If voltage exceeds the specified maximum, contact your utility or adjust the supply.
  • Inspect wiring: With power OFF, verify that conductors are landed on the correct terminals and that no extra phases are connected. Tighten all lugs to specified torque.
  • Check for surges: If E04 appears during storms or when large loads switch on/off, consider installing a surge protective device (SPD) upstream.

If supply voltage is within spec and E04 persists, the internal voltage sensing circuit on the main control board may be defective and require board replacement.

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Repair Difficulty

Hard 4/5

Required Part

Main Control Board
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