Furnace short cycles, turning on and off every few minutes

Safety first: Turn off power before removing panels.

• Step 1 – Replace filter: Install a new filter of the correct size and MERV rating.
• Step 2 – Check thermostat location: Ensure thermostat is not near supply registers, space heaters, or direct sunlight. Relocation may be needed.
• Step 3 – Observe furnace: Watch a cycle with the blower door on. If burners shut off quickly and blower continues, the limit may be opening. Improve airflow by opening registers and checking ducts.
• Step 4 – Professional check: A technician should measure temperature rise and inspect for oversizing or duct issues.