MUSTART
External Breaker Trip / High Inrush or Ground Leakage
Charger trips the upstream breaker or GFCI immediately when starting a charge, but no error appears on the charger display.
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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
Breaker undersized for charger setting, nuisance tripping of GFCI breaker, ground leakage from charger cable, shorted internal component on main control board
How to Fix / Troubleshooting
Safety warning: Repeatedly resetting a tripping breaker without finding the cause is unsafe.
- Check charger current setting: Ensure the MUSTART charger is set to no more than 80% of the breaker rating (e.g., 32 A max on a 40 A breaker).
- Inspect cable: Look for damage along the cable that could cause leakage to ground.
- Try a non‑GFCI breaker (if code‑compliant): Some installations use a GFCI breaker plus EVSE GFCI, which can cause nuisance trips. Consult an electrician about proper configuration.
- Persistent trips: If the breaker trips even at reduced current and with intact cable, an internal short or leakage on the main control board is likely and requires service.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board or Charging Cable Assembly
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