Furnace emits a metallic or rattling noise when the blower starts or stops.

Safety: Turn off power before tightening screws or working near moving parts.

Steps:

• Check that the blower and burner compartment doors are properly seated and latched. Tighten any loose screws.
• Inspect nearby ductwork for loose joints or sheet metal that flexes when the blower runs. Secure with screws and foil tape as needed.
• Ensure the vent pipe is properly supported and not rattling against other objects.
• Run the furnace and listen carefully to pinpoint the source, then secure or pad the area as appropriate.