OEM Lennox Limit Switch w/ Manual Reset — 93J39

The genuine OEM Lennox 93J39 limit switch with manual reset is a critical safety component that monitors temperature inside your furnace or air handler. If the heat exchanger area exceeds a safe threshold, this high-limit switch opens the circuit to shut down the burners and prevent overheating, protecting your equipment and home from damage.

Common failure symptoms: A tripped or failed 93J39 may cause the furnace to stop heating entirely, cycle on the limit repeatedly, or refuse to restart until manually reset. Because this is a manual-reset device, a persistent trip usually signals restricted airflow, a dirty filter, or a blower problem — but a switch that will not reset or has failed open must be replaced.

Why OEM matters: The 93J39 is calibrated to the specific trip and reset temperatures required by your Lennox system's design. Genuine OEM parts ensure the correct temperature rating, mounting, and terminal fit so the safety circuit performs exactly as engineered. Substituting a generic switch with the wrong set point risks nuisance shutdowns or, worse, failure to protect against a real overheat condition.