{"product_id":"oem-lennox-flame-sensor-20j91","title":"OEM Lennox Flame Sensor — 20J91","description":"\u003cp\u003eThe genuine OEM Lennox \u003cstrong\u003e20J91\u003c\/strong\u003e flame sensor is the safety device that confirms your burners have actually lit during each heating cycle. Using flame rectification, the sensor generates a small microamp current when it detects the presence of flame and signals the control board to keep the gas valve open. Without a valid flame signal, the board closes the valve within seconds to prevent unburned gas from accumulating.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCommon failure symptoms:\u003c\/strong\u003e A dirty or worn \u003cstrong\u003e20J91\u003c\/strong\u003e is one of the most frequent causes of a furnace that lights briefly then shuts off (short cycling), repeated ignition retries and hard lockouts, or intermittent no-heat calls. Oxidation and carbon buildup on the sensor rod weaken the flame signal over time.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy OEM matters:\u003c\/strong\u003e The rod length, mounting geometry, and alloy of the \u003cstrong\u003e20J91\u003c\/strong\u003e are engineered for correct flame immersion in your specific Lennox burner assembly. A mismatched aftermarket sensor can sit in the wrong part of the flame, produce an unstable microamp reading, or corrode prematurely. The factory OEM part restores a strong, stable flame signal and dependable ignition.\u003c\/p\u003e","brand":"Lennox","offers":[{"title":"Default Title","offer_id":63081113223539,"sku":"LNX-20J91","price":19.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-flame-sensor-straight-LNX-20J91.jpg?v=1783761016","url":"https:\/\/nationalhvacparts.com\/products\/oem-lennox-flame-sensor-20j91","provider":"National HVAC Parts","version":"1.0","type":"link"}