OEM Lennox Limit Switch — 39L08

The genuine OEM Lennox 39L08 limit switch is a temperature-sensing safety control mounted in your Lennox furnace that monitors heat-exchanger and plenum temperatures. If the furnace overheats — typically from restricted airflow — the switch opens the circuit to shut down the burners and protect the equipment from damage and fire risk.

A failing or nuisance-tripping limit switch commonly causes the furnace to short-cycle, shut off before reaching the set temperature, run the blower continuously, or lock out with no heat. A switch stuck open leaves you with no heat, while one stuck closed defeats a critical safety function.

Using the OEM Lennox 39L08 is essential for safety-rated components: it's calibrated to the exact open and close temperatures your furnace requires. An incorrect aftermarket switch can trip early, fail to trip when needed, or fit improperly. This factory-direct replacement restores proper overheat protection and reliable operation to your Lennox system.