Furnace runs but some rooms are too cold while others are too warm.

Safety: Turn off power before reaching into duct openings.

Steps:

• Check registers: Open registers in cold rooms fully and partially close registers in overly warm rooms.
• Inspect dampers: If there are manual dampers on branch ducts, adjust them to balance airflow.
• Replace filter: Ensure the filter is clean to maximize airflow.

Note: Persistent imbalance may require duct modifications by an HVAC contractor.