Furnace is very loud at the return grille; whistling or roaring sound.

Safety first: Turn off power before changing filters or opening panels.

Homeowner checks:

• 1. Replace filter with proper type: Avoid overly restrictive high-MERV filters unless the duct system is designed for them. Use a filter type recommended for your Philco furnace.
• 2. Open return grilles: Ensure all returns are unobstructed.
• 3. Check for furniture or drapes blocking airflow: Move items away from returns.

When to call a professional: A technician can measure static pressure, adjust blower speed on the Philco control board, and recommend duct modifications.