OEM Lennox Limit Switch — 36K29
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The genuine OEM Lennox 36K29 limit switch is a thermally activated safety device that guards your furnace against dangerous overheating. Positioned to sense heat exchanger or plenum temperature, it interrupts the gas valve circuit whenever the supply air rises above the factory-set safe limit, most often due to blocked filters, closed registers, or a weak blower motor. It is a key line of defense for your Lennox heating system.
Common failure symptoms: When the 36K29 degrades it may open too early, producing short cycling and inconsistent heat, or stick open and block ignition entirely. Watch for the blower running without heat, repeated lockouts, or a high-limit fault indicated on the control board.
Why OEM matters: Each Lennox limit switch is set to a model-specific trip point. Installing an aftermarket switch with the wrong calibration invites nuisance trips or leaves the heat exchanger unprotected. The OEM Lennox 36K29 delivers the exact rating and mounting your furnace was designed for.
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