Walli charger displays E03 and refuses to start; app may show 'Line/Neutral reversed or missing ground'.

Safety first: This is a mains wiring issue. If you are not a licensed electrician, do not attempt internal wiring changes.

Diagnostic steps:

• Turn off power at the breaker dedicated to the Walli charger and lock it out if possible.
• Open the Walli base plate: Remove the front cover to access the supply terminal block. Do not touch any capacitors or control board components.
• Verify wiring order: Confirm that the conductors are connected according to the Walli installation diagram: typically L (or L1/L2/L3), N, and PE in the correct positions. Tighten terminal screws to the torque specified in the manual.
• Check earth continuity: Ensure the PE conductor is present, correctly sized, and firmly clamped. The metal backplate (if present) should be bonded to earth via the designated screw.
• Upstream check: If wiring inside the Walli is correct, have an electrician verify polarity and earth continuity at the supply panel and any junction boxes using a proper tester.
• Restore power and test: After corrections, reassemble the unit, restore power, and check if E03 clears. If the error persists with verified wiring, the internal supply monitoring circuit on the Walli control board may be faulty and require replacement.