{"product_id":"oem-lennox-pressure-switch-w-bracket-34m74","title":"OEM Lennox Pressure Switch w\/ Bracket — 34M74","description":"\u003cp\u003eThe \u003cstrong\u003e34M74\u003c\/strong\u003e is a genuine OEM Lennox pressure switch supplied with its factory mounting bracket. This safety switch monitors the negative pressure created by the inducer\/draft blower and confirms that combustion air and flue venting are flowing correctly before the furnace allows the igniter and gas valve to fire. It is a critical combustion-air-proving safety control on your Lennox furnace.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCommon failure symptoms:\u003c\/strong\u003e A furnace that ignites briefly then shuts down, the inducer motor running but the burners never lighting, or a control-board fault code indicating an open or stuck pressure switch. A failed switch, cracked hose, or blocked port prevents the system from proving draft, locking the furnace out on safety to protect against a blocked vent or flue.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy OEM matters:\u003c\/strong\u003e Pressure switches are calibrated to a specific trip point (in inches of water column) matched to your Lennox furnace model and venting configuration. An incorrect or aftermarket switch with the wrong setpoint may fail to prove draft or, worse, allow firing under unsafe venting conditions. The exact OEM \u003cstrong\u003e34M74\u003c\/strong\u003e switch and bracket ensure the correct pressure calibration, secure mounting, and safe, code-compliant operation.\u003c\/p\u003e","brand":"Lennox","offers":[{"title":"Default Title","offer_id":63081089663347,"sku":"LNX-34M74","price":24.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-pressure-switch-single-LNX-34M74.jpg?v=1783762944","url":"https:\/\/nationalhvacparts.com\/products\/oem-lennox-pressure-switch-w-bracket-34m74","provider":"National HVAC Parts","version":"1.0","type":"link"}