E18 appears; charger indicates insulation resistance or isolation fault.

Safety first: Isolation faults can present a shock hazard. Turn off power and do not use the charger until resolved.

• Check for water ingress: Inspect the enclosure seals, cable glands, and conduit entries for signs of water. Dry the interior thoroughly and correct any sealing issues.
• Inspect wiring: Look for nicks, cuts, or crushed insulation on internal conductors, especially where they pass through metal openings.
• Clean PCB: If there is visible contamination (dust, insects, residue) on the PCB, clean carefully with electronics-safe cleaner and allow to dry completely.

If E18 persists after drying and inspection, the insulation monitoring circuit or main control board may require replacement.