Wallbox unit shows 'Error 04' and does not initiate charging; often associated with contactor or relay failure.

Safety first: Turn off the upstream breaker and verify absence of voltage before opening the charger. Do not attempt to free a stuck contactor while energized.

• Power cycle test: Turn the breaker OFF for 2–3 minutes, then ON. Listen carefully when starting a charge: you should hear a distinct click from the internal contactor. If no click is heard and Error 04 appears, continue below.
• Check for overheating signs: If the charger housing feels unusually hot, allow it to cool completely before further inspection. Overheating can cause contactor damage.
• Internal inspection (qualified technician): Open the Wallbox and locate the main power contactor. Inspect for discoloration, melted plastic, or burnt smell. Verify that the coil wires and feedback wires are firmly seated in their terminals.
• Contactor coil test: With power disconnected, measure the resistance of the contactor coil and compare with manufacturer specs. An open or shorted coil indicates the contactor must be replaced.
• Feedback circuit check: Confirm that the auxiliary contacts or feedback wires from the contactor to the main control board are intact. A broken feedback loop can trigger Error 04 even if the contactor operates.

Replace the main power contactor or the main control board if tests confirm failure. This repair should be performed by a qualified service technician.