OEM Lennox Furnace Limit Switch — 73K18
OEM Guaranteed
Same-Day Ship
30-Day Returns
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The genuine OEM Lennox 73K18 is a furnace high-limit safety switch engineered to protect your Lennox heating system from overheating. It senses the temperature near the heat exchanger and, if it climbs past the factory-set trip point, the 73K18 disconnects power to the burners or gas valve to shut down the heat cycle, resetting automatically once temperatures normalize. This protective control appears on numerous Lennox gas furnaces and air handling units.
Common failure symptoms: Typical signs of a failing limit switch include short cycling, intermittent or no heat, a blower motor that runs nonstop, and limit-fault lockouts at the furnace control. Prolonged thermal cycling can cause the internal contacts to stick or the trip temperature to drift out of specification.
Why OEM matters: The 73K18 is calibrated to a model-specific trip and reset temperature, so a mismatched substitute can jeopardize safety or cause nuisance shutdowns. Installing the OEM 73K18 ensures the precise calibration, terminal layout, and secure fit your Lennox furnace requires for safe, consistent heating.
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