Furnace cycles on and off very quickly (every 1–5 minutes) without reaching thermostat setpoint.

Safety first: Turn off power before removing thermostat cover.

• Thermostat location: Ensure the thermostat is not directly above a supply register or in direct sunlight.
• Adjust cycle rate: On programmable thermostats, set the heating cycle rate to the recommended setting for gas furnaces (often 3–5 cycles per hour).
• Airflow checks: Replace filter and open registers to reduce overheating-related cycling.

If the furnace is significantly oversized, only a system redesign can fully correct short cycling.