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The genuine OEM Lennox Y8805 pressure switch is a draft-proving safety control that verifies correct combustion airflow before your Lennox furnace fires. Working with the draft inducer motor, it senses the negative pressure in the venting system and closes its contacts only when safe airflow is confirmed — a required step in the ignition sequence that protects against improper venting and flue-gas spillage.
Common failure symptoms: the furnace not lighting despite a running inducer, ignition lockouts, intermittent no-heat calls, or a control board reporting an open or stuck pressure switch. Common causes include a clogged pressure tube, blocked vent or drain, a failing inducer, or a switch diaphragm that no longer trips at the proper pressure.
Why OEM matters: the Lennox Y8805 is calibrated to the exact pressure setpoint your furnace was designed around. Non-OEM switches with different thresholds can permit unsafe operation or cause frustrating nuisance lockouts. The factory-specified part delivers accurate draft verification, reliable safety performance, and guaranteed compatibility with your Lennox system.