Furnace runs but some rooms are much colder than others

Safety first: Turn off power before removing panels; duct adjustments can be done with furnace off.

• Check registers: Ensure supply registers in cold rooms are fully open and not blocked by furniture or rugs.
• Filter replacement: Replace a dirty filter to restore full airflow.
• Balance dampers: If your duct system has manual dampers, slightly close dampers feeding overheated rooms and open those to colder rooms. Make small adjustments and test over several cycles.
• Professional duct evaluation: Persistent imbalance may require duct resizing or additional returns, which should be designed by an HVAC professional.