Furnace short cycles, turning on and off frequently without reaching temperature.

Safety first: Turn off power before removing panels or filters.

Homeowner checks:

• 1. Replace air filter: Install a clean filter to ensure proper airflow.
• 2. Open all vents: Make sure supply and return vents are open and not blocked by furniture or rugs.
• 3. Check thermostat location: If the thermostat is near a heat source (sunlight, lamp, register), it may sense heat too quickly. Redirect airflow away from the thermostat or consult about relocating it.
• 4. Observe furnace operation: Note whether the burners shut off due to limit trips (blower continues running) or if the thermostat is turning the furnace off prematurely.

When to call a professional: Persistent short cycling can damage the heat exchanger. A technician should check for high limit trips, verify duct sizing, and adjust blower speed or gas input on the Philco furnace.