Lennox 71W43 Limit Switch

The Lennox 71W43 Limit Switch is a critical safety component designed for precise thermal regulation within residential and commercial furnace assemblies. This OEM Lennox replacement part, also identified as the L140-30F limit control, is engineered to monitor heat exchanger temperatures and interrupt the electrical circuit if internal heat exceeds safe parameters. With a fixed 140°F opening temperature and a 110°F automatic reset, this switch ensures the blower continues to dissipate residual heat until the plenum reaches a stabilized state. The 102857-03 limit switch features a robust 5-inch overall length and a left-hand orientation for seamless integration into the factory mounting position. Built for durability in high-demand environments, this high-temperature furnace limit provides the reliable circuit-breaking performance necessary to prevent equipment damage and ensure system safety during peak heating cycles. Verify the "L140-30F" stamping on your existing control to confirm a direct match for this automatic reset limit switch.

• Precise Thermal Calibration: Factory-set to open at 140°F and close at 110°F (30°F differential) for accurate furnace protection.
• OEM Compatibility: Replaces Lennox, Armstrong, Ducane, and Allied Air part number 102857-03 without the need for mounting modifications.
• Automatic Reset Logic: Eliminates the need for manual intervention once the heat exchanger has cooled to a safe operating temperature.
• Durable Construction: Built with a green sleeve indicator and high-grade materials to withstand corrosive environments and repetitive thermal cycling.

• What causes a "Limit Switch Open" fault code? This often indicates restricted airflow, such as a clogged furnace filter, a failing blower motor, or an undersized duct system causing the unit to trip the 71W43 limit.
• Can I use a higher temperature limit if this one keeps tripping? No. You must always match the L140-30F specifications. Increasing the limit threshold can lead to heat exchanger failure or a fire hazard.
• Is the 71W43 compatible with other brands? This part is a direct cross-reference for several Allied Air brands (Armstrong, Ducane, Concord) using the 102857-03 part number.

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Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.