Charger emits a loud humming or buzzing noise during operation, louder than normal transformer hum.

Safety first: Turn off power before tightening any internal components.

• Identify source: Listen carefully to locate whether the noise comes from the contactor, transformer, or enclosure panels.
• Tighten hardware: With power off, tighten mounting screws for the contactor, transformers, and enclosure panels.
• Check for resonance: Add appropriate vibration-damping washers or pads where panels vibrate, following Autel guidelines.
• Monitor temperature: Ensure the noisy component is not overheating; if it is, have a technician evaluate for overload or impending failure.