OEM Lennox Limit Switch — 57W38

The genuine OEM Lennox 57W38 limit switch is a temperature-sensing safety control mounted in the heat-exchanger airflow path of Lennox gas furnaces. It protects the system from overheating by cutting power to the gas valve whenever supply-air temperature climbs above its rated set point — typically caused by restricted airflow from a dirty filter, a failing blower motor, or closed registers. Once temperatures return to normal the switch resets and allows the furnace to fire again.

Common failure symptoms: Short-cycling on heat, the burners igniting then dropping out repeatedly, no heat with the blower still running, or a limit/overheat code on the control board. A limit switch that has drifted out of calibration or failed open will keep the furnace from staying lit.

Why OEM matters: The Lennox 57W38 is matched to the precise trip and reset temperatures your furnace was designed for. An off-spec aftermarket switch can nuisance-trip or fail to open when it should, risking heat-exchanger damage. Choosing the factory part guarantees correct fit and reliable overheat protection for your Lennox equipment.