Unit emits a metallic rattling noise when heating but not when idle.

Safety first: Unplug and cool the unit before opening.

Inspection:

• Remove the cover and inspect the heater shield and surrounding panels.
• Look for loose screws or brackets that can vibrate when heated.

Corrective action:

• Tighten all accessible screws on the heater shield and internal frame.
• If a panel is warped and contacts other metal when hot, gently adjust its position or replace the heater shield.