E04
FLO
AC Line Overvoltage Protection
Charger displays E04 / ‘Overvoltage’ and will not start charging.
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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 supply voltage above specification, Miswired service (e.g., 277 V line on residential charger), Faulty AC voltage sensing circuit on control board
How to Fix / Troubleshooting
Safety first: Only a licensed electrician should measure line voltage inside the panel or charger. Turn OFF the breaker before opening any covers.
- Check supply voltage: Have an electrician measure line-to-line and line-to-ground voltage at the charger input. Compare to FLO’s specified operating range (typically around 208–240 V AC for home units).
- Verify correct circuit: Ensure the charger is connected to a 240 V residential circuit, not a 277 V or other high-voltage leg.
- Inspect neutral/ground bonding: Confirm the panel is wired correctly and that there are no shared neutrals or improper bonds that could affect sensing.
- Power-cycle: After any corrections, turn the breaker OFF for 2 minutes, then ON, and test again.
- If voltage is within spec but E04 persists: The AC voltage sensing circuit on the main control board may be defective. Replacement of the control board is typically required.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control Board
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