OEM Lennox Limit Switch — 33J84
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The genuine OEM Lennox 33J84 limit switch is a critical safety control in your Lennox gas or electric furnace. Mounted on the heat exchanger or in the plenum, it continuously monitors supply-air temperature and interrupts the burner or heating element if the furnace overheats — protecting the heat exchanger, wiring, and your home from dangerous conditions. This part is engineered to the exact temperature trip points Lennox specifies for your unit.
Common failure symptoms include short cycling (the furnace repeatedly starts and stops), the blower running continuously, no heat despite the burners igniting, or the system locking out on a limit fault. A limit switch that trips prematurely or fails open will prevent normal operation, while one stuck closed removes an essential safety layer.
Why OEM matters: the 33J84 is calibrated to the precise open/close temperatures and physical mounting of your Lennox furnace. Universal or aftermarket switches with the wrong trip point can allow overheating or cause nuisance shutdowns. Choosing the factory-specified Lennox part ensures correct fit, reliable protection, and continued compliance with your equipment's design ratings.
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