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The Lennox 56M04 is a genuine OEM pressure switch that verifies proper draft and venting before your Lennox furnace ignites. It senses the negative pressure created by the inducer motor and confirms the flue is clear, allowing the ignition sequence to proceed only when it is safe to do so. This switch is calibrated to Lennox factory specifications for the exact pressure setpoint your furnace requires.
Common failure symptoms include a furnace that runs the inducer but never lights, repeated lockouts, a pressure switch fault code on the control board, or the burners igniting briefly then shutting off. A stuck-open switch blocks ignition, while a stuck-closed switch defeats an essential safety check against blocked or improper venting.
Why OEM matters: Pressure switches are matched to the specific inducer and vent design of each Lennox furnace, and even a small deviation in the setpoint can cause nuisance faults or unsafe operation. The genuine 56M04 guarantees the correct pressure rating and hose connection, restoring reliable ignition and preserving the safety and warranty of your Lennox system.