{"product_id":"oem-lennox-limit-switch-56w21","title":"OEM Lennox Limit Switch — 56W21","description":"\u003cp\u003eThe genuine OEM Lennox \u003cstrong\u003e56W21\u003c\/strong\u003e limit switch is a high-temperature safety control for your Lennox gas furnace. Positioned to read heat-exchanger and plenum temperatures, it opens the burner circuit whenever operating heat climbs past the safe limit, protecting the furnace from damage due to restricted airflow, clogged filters, or a failing blower motor. Each \u003cstrong\u003e56W21\u003c\/strong\u003e is factory-calibrated to the trip point specific to your Lennox model.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCommon failure symptoms:\u003c\/strong\u003e A failing \u003cstrong\u003e56W21\u003c\/strong\u003e typically shows up as short cycling, nuisance high-limit lockouts, or a furnace that heats briefly then shuts off. You may also experience the blower running continuously, inconsistent heat output, or complete no-heat lockouts after multiple failed cycles.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy OEM matters:\u003c\/strong\u003e Because the limit switch is a safety-critical part, its calibration must be exact. Universal replacements with incorrect trip temperatures risk either unnecessary shutdowns or inadequate overheat protection for the heat exchanger. The OEM \u003cstrong\u003e56W21\u003c\/strong\u003e guarantees the precise temperature rating, electrical connections, and physical fit your Lennox equipment demands for safe, reliable heating.\u003c\/p\u003e","brand":"Lennox","offers":[{"title":"Default Title","offer_id":63081102279027,"sku":"LNX-56W21","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-56W21.jpg?v=1783762576","url":"https:\/\/nationalhvacparts.com\/products\/oem-lennox-limit-switch-56w21","provider":"National HVAC Parts","version":"1.0","type":"link"}