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The genuine OEM Lennox 92L21 pressure switch is a critical safety control that confirms the draft inducer is producing proper venting airflow before the furnace is allowed to ignite. It monitors negative pressure in the vent system and closes to prove draft, protecting your Lennox equipment from unsafe combustion conditions.
Common failure symptoms: furnace that clicks but never lights, repeated ignition lockouts, a control board flashing a pressure-switch fault code, or short cycling. A stuck-open or stuck-closed switch, cracked diaphragm, or clogged sensing port are typical culprits.
OEM matters here because the 92L21 is calibrated to a specific trip pressure matched to your Lennox inducer and venting design. An incorrect switch can allow ignition without adequate draft or block heating entirely with false faults. This factory part restores accurate, safe pressure sensing and keeps your furnace's safety sequence intact.