OEM Lennox Limit Switch — 57W37

The genuine OEM Lennox 57W37 limit switch is a high-temperature safety control used in Lennox gas furnaces to guard the heat exchanger against overheating. Positioned in the heated-air stream, it opens the control circuit and shuts off the gas valve when discharge-air temperature exceeds its factory set point — a condition usually triggered by low airflow from a clogged filter, weak blower motor, or blocked ductwork. It closes again automatically once the furnace cools.

Common failure symptoms: Repeated short-cycling, burners that ignite and then shut down after a minute or two, no heat while the blower continues to run, or an open-limit fault on the control board. A worn or out-of-calibration switch will interrupt normal heating cycles even when the furnace is operating properly.

Why OEM matters: The Lennox 57W37 is engineered to the exact trip and reset thresholds your furnace requires. Substituting a generic switch with a different set point can cause nuisance lockouts or leave the heat exchanger unprotected. The factory-matched component ensures a proper fit and dependable safety response for your Lennox system.