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The genuine OEM Lennox 11U72 pressure switch, supplied complete with its mounting bracket, is a critical safety device in your Lennox furnace. It senses the negative pressure created by the inducer motor to confirm that the venting system is clear and that combustion gases are being exhausted properly before the furnace is allowed to ignite.
Common failure symptoms: A faulty or stuck pressure switch commonly causes the furnace to fail to start, lock out on a pressure-switch fault code, or short-cycle. A clogged pressure hose, a weak inducer, a blocked vent, or a switch that no longer closes at the correct pressure will all trip this safety and halt operation.
Why OEM matters: Pressure switches are calibrated to a specific trip point matched to your furnace's inducer and venting design. The OEM 11U72 arrives pre-set to the correct pressure rating with the proper bracket for a direct fit — an aftermarket switch with the wrong calibration can allow unsafe operation or cause persistent nuisance lockouts. Choosing OEM protects both safety and your Lennox warranty.