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The genuine OEM Lennox 15M20 is a furnace pressure switch supplied with its mounting bracket for direct, hassle-free installation in your Lennox gas furnace. This safety control monitors negative pressure created by the draft inducer motor to confirm the venting system is clear and combustion gases are being properly exhausted. Only when the 15M20 senses adequate draft will it close its contacts and permit the furnace to proceed to ignition.
Common failure symptoms: The inducer motor energizes but the igniter and burners do not fire, the furnace repeatedly locks out on a pressure-switch code, or heating is intermittent. Typical causes include a failed diaphragm, blocked or cracked sensing hose, condensate in the tubing, or a switch that no longer actuates at its rated setpoint.
Why OEM matters: This switch is calibrated to a specific pressure threshold and the included bracket ensures correct positioning and hose routing on your Lennox unit. The factory 15M20 guarantees the right activation point and mechanical fit — a generic replacement with the wrong calibration or mounting can cause false trips or compromise safe combustion. Choose the genuine OEM assembly for reliable draft verification and proper installation in your Lennox equipment.