Wallbox display shows E04; charging does not start; upstream breaker may trip intermittently.

Critical safety warning: This fault can indicate a serious internal short. Turn off the dedicated breaker and lock it out if possible. Do not re-energize repeatedly.

• External check: Inspect the supply cable from the distribution board to the wallbox for visible damage, overheating, or discoloration at the entry point.
• Internal inspection: With power isolated, remove the wallbox cover. Look for burned insulation, melted plastic near the power contactor, or darkened terminal blocks.
• Tighten terminals: If no severe damage is visible, gently check that all L1/L2/L3/N/PE terminals are tight using an insulated screwdriver, following the torque values in the Mercedes-Benz installation manual.
• Do NOT bypass components: Never bypass the power contactor or surge protection to ‘test’ the unit. This is dangerous and voids safety certifications.
• Professional repair: Any signs of burning, melted parts, or repeated E04 after tightening connections require replacement of the power contactor, terminal block, or surge module by a qualified technician. The unit should undergo insulation and continuity testing before being returned to service.