OEM Lennox Limit Switch — 51M75
OEM Guaranteed
Same-Day Ship
30-Day Returns
Secure Checkout
The genuine OEM Lennox 51M75 limit switch is a critical safety component in your furnace's heat exchanger circuit. It continuously monitors plenum temperature and cuts power to the burners if the system overheats, protecting your heat exchanger and household from dangerous conditions. This factory-spec switch is engineered to the exact temperature trip and reset points your Lennox equipment requires.
Common failure symptoms: When the 51M75 fails or drifts out of calibration, you may notice short-cycling (the furnace repeatedly firing and shutting off), no heat despite the blower running, or a unit that trips on limit and locks out. A cracked or worn switch can also cause intermittent operation that's hard to diagnose.
Why OEM matters: Aftermarket limit switches often trip at incorrect temperatures, which either allows unsafe overheating or causes nuisance shutdowns. The OEM Lennox 51M75 guarantees the correct trip setpoint, terminal configuration, and mechanical fit for a reliable, code-compliant repair that keeps your Lennox furnace running safely.
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