Why Your Furnace Short-Cycles (and How to Stop It)
Short-cycling wastes gas and wears out your furnace — the usual suspects are airflow, the flame sensor, and oversizing.
Short-cycling is when your furnace turns on and off too frequently. It drives up bills and shortens equipment life, so it's worth diagnosing promptly.
Airflow and the flame sensor
Restricted airflow from a dirty filter or closed vents makes the furnace overheat and shut off early. A dirty flame sensor can also cause the burners to drop out seconds after ignition.
Oversizing and thermostat placement
An oversized furnace heats the air near the thermostat quickly and shuts off before the whole home is warm. A thermostat in direct sun or near a vent can cause the same pattern.
Key takeaways
- Replace the filter and open all vents
- Have the flame sensor cleaned during servicing
- Keep the thermostat away from heat sources
- Right-size the furnace at replacement time
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