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The genuine OEM Lennox 71K11 pressure switch kit proves that the draft inducer is moving combustion air and venting flue gases before the furnace allows ignition. This safety control senses negative pressure through its sampling tube and closes its contacts to permit the ignition sequence, protecting against blocked vents and inducer failures.
Common failure symptoms: the furnace won't ignite, the inducer runs but the burner never lights, a pressure-switch-open fault code, short-cycling, or hard lockouts — often worsened by a cracked hose, clogged port, or condensate blockage that the kit's fresh tubing helps resolve.
Why OEM matters: the switch's trip pressure is calibrated to your Lennox furnace's inducer and vent design; even small deviations cause nuisance faults or unsafe operation. The OEM Lennox 71K11 kit includes the correctly rated switch and matched hardware for a precise, reliable fit that generic switches can't guarantee.