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The genuine OEM Lennox 14A39 pressure switch kit is a critical safety control that confirms proper venting before your furnace ignites. It senses the negative pressure created by the inducer motor and only closes to allow ignition when airflow through the flue is adequate. This prevents the furnace from firing with a blocked vent or failed draft inducer, protecting your home from dangerous flue-gas spillage.
A failing or fouled pressure switch is one of the most common causes of a furnace that ignites briefly and then shuts down, or won't light at all. Symptoms include repeated ignition lockouts, the inducer running without the burners firing, or error codes indicating an open pressure switch. Cracked tubing and moisture in the switch port produce the same faults.
The OEM 14A39 kit is calibrated to the exact trip point your Lennox furnace requires. Generic switches with the wrong pressure setpoint can either lock out a healthy furnace or, worse, allow it to run unsafely. Trust this factory-spec part to restore reliable, safe ignition sequencing.