OEM Lennox Limit Switch — 10M74
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The genuine OEM Lennox 10M74 limit switch is a critical safety control mounted on the heat exchanger of your Lennox furnace. It continuously monitors supply-air temperature and interrupts the gas burner circuit if the furnace overheats — typically caused by restricted airflow, a dirty filter, or a failed blower motor. This protects the heat exchanger from cracking and prevents dangerous operating conditions.
Common failure symptoms: A furnace that short-cycles (heats briefly then shuts off), no heat despite a running blower, repeated tripping on high limit, or a burner that fails to light. Over time the bimetal element can weaken, stick, or open at the wrong temperature, causing nuisance lockouts.
Why OEM matters: The Lennox 10M74 is calibrated to the exact trip temperature and mounting specification of your equipment. Aftermarket substitutes with different set points can trip early, run long, or fail to protect the heat exchanger. Choosing the factory part guarantees correct fit, rated calibration, and preserves your Lennox warranty coverage.
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