Charger makes loud humming or buzzing noises during charging, louder than typical contactor click and transformer hum.

Safety first: Unusual mechanical noise can indicate impending failure. Isolate power before touching internal components.

• Identify source: With the cover on, listen carefully to locate the area of the noise (top, bottom, left, right).
• Inspect mounting (power off): Open the enclosure and check that the contactor and any transformers are firmly screwed to the DIN rail or backplate.
• Check supply voltage (electrician only): Low coil voltage can cause chattering. Measure control voltage at the contactor coil when energised.
• Tighten panels: Ensure the enclosure cover and any internal plates are securely fastened to reduce resonance.
• Replace noisy contactor: If the contactor buzzes excessively despite correct voltage and mounting, replace it with a Rolec‑approved equivalent.