OEM Lennox Limit Switch — 18K80
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The genuine OEM Lennox 18K80 limit switch is a high-temperature safety control that protects your Lennox furnace from overheating. Mounted near the heat exchanger, it continuously senses supply-air temperature and shuts off the burners if the furnace exceeds a safe threshold — typically caused by restricted airflow. As a direct factory replacement, the 18K80 opens and resets at the precise temperatures specified for your Lennox model.
Common Failure Symptoms
- Furnace short-cycles, firing then shutting off on high limit
- Blower runs continuously while burners stay off
- No heat with a limit-related fault code
- Overheating due to a switch that fails to reset properly
A tripped or failed limit switch is a common no-heat complaint and an important indicator of airflow problems such as a clogged filter or blocked ductwork.
Why OEM Matters
Because a limit switch is a primary safety device, correct trip and reset temperatures are essential. Generic switches with the wrong ratings can nuisance-trip or fail to protect the heat exchanger. The OEM Lennox 18K80 is calibrated to factory specifications, ensuring exact fit, dependable overheat protection, and safe operation of your Lennox equipment.
Shipping Information
- Orders placed before 3PM CST ship same business day
- Standard delivery: 2-5 business days
- Express shipping available at checkout
- Free shipping on orders over $75
- Tracking number emailed upon shipment
Return Policy
- 30-day returns on unused parts in original packaging
- Electrical parts (capacitors, contactors, control boards) are final sale once installed
- Email info@nationalhvacparts.com to initiate a return
- Refunds processed within 5-7 business days