OEM Lennox Furnace Pressure Switch — 49L90
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The genuine OEM Lennox 49L90 pressure switch safeguards your furnace by verifying proper combustion airflow before ignition is permitted. It reads the negative pressure generated by the draft inducer motor and confirms that flue gases are venting correctly. When conditions are safe, the switch closes to allow the ignition sequence; when airflow is restricted or the inducer underperforms, it opens and locks out the burners to protect your home.
Common failure symptoms: A furnace that starts and immediately shuts off, repeated ignition lockouts, no heat despite the inducer running, or a diagnostic code pointing to the pressure switch. Blocked ports, a leaking sensing hose, or a fatigued internal diaphragm commonly trigger these faults.
Why OEM matters: Lennox calibrates each pressure switch to a model-specific trip point tied to the furnace's venting characteristics. A substitute with the wrong pressure rating can cause false lockouts or bypass an essential safety check. The OEM 49L90 ensures the correct calibration, connector, and fit engineered for 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