OEM Lennox Limit Switch — 39L06

The genuine OEM Lennox 39L06 limit switch is a critical high-temperature safety control found in Lennox gas and electric furnaces. It continuously monitors the temperature in the heat exchanger and plenum area, shutting off the burners if the unit overheats to prevent damage and hazardous conditions. This factory-spec switch is calibrated to the exact trip and reset temperatures your Lennox equipment requires for safe, reliable operation.

Common failure symptoms include short-cycling (the furnace turns on and off repeatedly), the blower running continuously, no heat output, or the furnace locking out entirely. A limit switch that has failed open or drifted out of calibration will trip prematurely, leaving you without reliable heat. Because the 39L06 is a safety-critical component, a faulty unit should be replaced promptly rather than bypassed.

Why OEM matters: Lennox designs its limit switches with precise temperature calibration matched to each furnace model's heat exchanger geometry and airflow. Generic aftermarket switches may trip at the wrong temperature, causing nuisance shutdowns or, worse, failing to protect the unit. Choosing the genuine OEM 39L06 guarantees correct fit, proper calibration, and full compatibility with your Lennox system.