Water heater vibrates excessively or rattles when the burner is on.

Safety: Turn off power and gas before tightening any internal components.

Steps:

• Check wall mounting: Ensure the Sime heater is firmly fixed to the wall bracket and that the bracket is secure.
• Tighten screws: Inspect and tighten accessible screws on the burner, fan, and casing panels.
• Inspect flue: Check that the flue is properly supported and not vibrating against walls or roof structures.

Professional help: If vibration is due to a failing fan or burner assembly, have a technician replace the affected parts.