Furnace rattles or vibrates loudly when running.

Safety: Turn off power before tightening or adjusting components.

• Check panels: Ensure all furnace access panels are properly seated and screws are tight.
• Inspect blower housing: Verify that the blower assembly mounting screws are tight and that the housing is not contacting the cabinet.
• Blower wheel balance: Spin the wheel by hand and look for wobble. If bent or damaged, the wheel should be replaced.
• Duct supports: Add or tighten duct hangers and use flexible connectors if necessary to reduce transmitted vibration.