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

Safety First: Turn off power before opening supply plenum or return connections.

• Adjust dampers: Locate manual dampers in branch ducts and partially close those serving overheated rooms to push more air to cooler rooms.
• Check returns: Ensure return grilles are not blocked and filters are clean.
• Inspect ducts near furnace: Look for disconnected or crushed ducts at the supply plenum and return drop.
• Professional balancing: For persistent imbalance, have an HVAC contractor perform a duct balancing and airflow test.