OEM Lennox Furnace Limit Switch — 49L89

The genuine OEM Lennox 49L89 limit switch is a high-temperature safety control that protects your furnace and home from overheating. Mounted near the heat exchanger or plenum, it continuously monitors supply air temperature. If heat builds up beyond a safe threshold — typically from restricted airflow or a blower problem — the switch opens and shuts off the burners to prevent damage to the heat exchanger and reduce fire risk.

Common failure symptoms: Frequent short-cycling on the limit, the furnace shutting down mid-cycle, no heat while the blower keeps running, or a control board reporting an open-limit fault. A switch that has tripped permanently or drifted out of calibration is a common culprit behind intermittent heating failures.

Why OEM matters: Lennox limit switches are set to a specific cut-out temperature matched to your furnace's design airflow and heat exchanger rating. An aftermarket switch with the wrong temperature setpoint can allow dangerous overheating or cause nuisance trips. The OEM 49L89 provides the exact temperature calibration and mounting fit your Lennox system was built for.