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The genuine OEM Lennox 36K28 limit switch is a temperature-activated safety control that keeps your furnace operating within safe limits. It senses the temperature of the heated air leaving the heat exchanger and cuts power to the gas valve if the furnace overheats — a condition usually triggered by restricted airflow or a failing blower. This protects both your equipment and your home.
Common failure symptoms: A worn or out-of-spec 36K28 can cause the furnace to short cycle, shut down mid-cycle, or refuse to ignite. Telltale signs include the blower running with no warm air, frequent safety lockouts, or a limit-open code from the ignition control.
Why OEM matters: The 36K28 is factory-calibrated to a precise trip temperature matched to your Lennox unit. Substitute switches with different ratings can create nuisance trips or fail to shut the system down when needed, risking heat exchanger damage. The OEM part ensures the correct setpoint and an exact, trouble-free fit.