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The genuine OEM Lennox 49M84 flame sensor is a critical safety component in your gas furnace. It uses flame rectification to confirm that the burners have ignited, signaling the control board to keep the gas valve open. Designed as a direct factory replacement, the 49M84 ensures precise fit and reliable flame detection for compatible Lennox furnaces.
Over time, oxidation and carbon buildup coat the sensor rod, weakening the microamp signal the furnace relies on. Typical symptoms include the furnace lighting and then shutting down after a few seconds, short cycling, repeated ignition lockouts, or the blower running with no heat. A failing flame sensor is one of the most common causes of no-heat calls in cold weather.
Aftermarket sensors often produce an out-of-spec flame signal that trips your furnace's safety logic, leading to nuisance lockouts. The OEM Lennox 49M84 is calibrated to your furnace's ignition control for consistent, code-compliant operation and long service life. Choosing genuine Lennox parts protects your equipment warranty and keeps your system running safely.