{"product_id":"oem-lennox-limit-switch-78w99","title":"OEM Lennox Limit Switch — 78W99","description":"\u003cp\u003eThe genuine OEM Lennox \u003cstrong\u003e78W99\u003c\/strong\u003e limit switch is a high-temperature safety control mounted near the heat exchanger of your Lennox furnace. It continuously monitors plenum temperature and shuts off the burners if the unit overheats — typically caused by restricted airflow — protecting the heat exchanger from cracking and preventing a fire hazard.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eSigns your limit switch may have failed:\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eFurnace repeatedly shuts off on high limit (short-cycling)\u003c\/li\u003e\n\u003cli\u003eBlower runs continuously and won't shut off\u003c\/li\u003e\n\u003cli\u003eNo heat, with the burners lighting briefly then extinguishing\u003c\/li\u003e\n\u003cli\u003eOverheating fault codes at the control board\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eBecause the \u003cstrong\u003e78W99\u003c\/strong\u003e is calibrated to a specific trip temperature matched to your Lennox furnace's design, installing the exact OEM part is essential for safe operation. A generic switch with the wrong setpoint can allow dangerous overheating or cause frustrating nuisance trips. Choose the factory \u003cstrong\u003e78W99\u003c\/strong\u003e to keep your Lennox furnace's built-in overheat protection working exactly as engineered.\u003c\/p\u003e","brand":"Lennox","offers":[{"title":"Default Title","offer_id":63081095201139,"sku":"LNX-78W99","price":19.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-limit-switch-snap-disc-LNX-78W99.jpg?v=1783762611","url":"https:\/\/nationalhvacparts.com\/products\/oem-lennox-limit-switch-78w99","provider":"National HVAC Parts","version":"1.0","type":"link"}