The furnace runs, but some rooms are too cold while others are too warm.

Safety first: Turn off power before accessing blower components.

• 1. Check registers and dampers: Make sure all supply registers and return grilles are open. Adjust manual dampers in branch ducts (if present) to direct more air to colder rooms.
• 2. Inspect filter and blower: Replace a dirty filter. Remove the blower assembly from the Thermia furnace and clean dust from the blower wheel blades to restore airflow.
• 3. Verify blower speed: On some Thermia models, blower speed taps or settings can be adjusted. A technician can increase heating speed to improve distribution.
• 4. Consider duct evaluation: If problems persist, have a professional assess duct design and insulation.