{"product_id":"oem-lennox-limit-switch-33h78","title":"OEM Lennox Limit Switch — 33H78","description":"\u003cp\u003eThe genuine OEM Lennox \u003cstrong\u003e33H78\u003c\/strong\u003e limit switch is a high-limit safety control that protects your furnace from overheating. Mounted near the heat exchanger, it continuously senses supply-air temperature and opens the circuit to shut off the burners if the plenum gets too hot — typically caused by restricted airflow. Once temperatures return to a safe range, the switch resets and normal operation resumes.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCommon failure symptoms\u003c\/strong\u003e include short cycling on heat, the burners shutting off while the blower keeps running, no heat despite the fan operating, or a furnace that trips out repeatedly. A limit switch stuck open causes no ignition, while one stuck closed defeats the safety function and can lead to dangerous overheating and heat exchanger damage.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy OEM matters:\u003c\/strong\u003e The \u003cstrong\u003e33H78\u003c\/strong\u003e is engineered with a precise temperature set point matched to your specific Lennox furnace. Using the correct factory switch guarantees the burners cut off at the safe design temperature, protecting the heat exchanger and your home. Aftermarket substitutes with incorrect trip temperatures can cause nuisance shutdowns or, worse, fail to protect the unit. Install the OEM \u003cstrong\u003e33H78\u003c\/strong\u003e for dependable overheat protection.\u003c\/p\u003e","brand":"Lennox","offers":[{"title":"Default Title","offer_id":63081109062003,"sku":"LNX-33H78","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-33H78.jpg?v=1783762510","url":"https:\/\/nationalhvacparts.com\/products\/oem-lennox-limit-switch-33h78","provider":"National HVAC Parts","version":"1.0","type":"link"}