Lennox 69W43 Flame Sensor

The Lennox 69W43 Flame Sensor is a critical OEM safety component engineered for precise flame rectification within gas furnace burner assemblies. As a direct 69W4301 replacement part, this sensor features a high-grade stainless steel sensing rod capable of withstanding operating temperatures up to 2190°F, paired with a durable ceramic insulator rated for 1000°F. When the furnace control board initiates the ignition sequence, the 69W43 detects the presence of the burner flame to ensure safe combustion. If the sensor fails to generate the necessary microamp signal due to carbon buildup or electrode degradation, the system will trigger an ignition lockout to prevent hazardous unburned gas accumulation. Designed for seamless HVAC part compatibility across Lennox, Armstrong, and Ducane units, this sensor utilizes a 90-degree offset rod geometry for optimal positioning in the burner’s path. For contractors performing furnace troubleshooting, replacing a fouled sensor with a new OEM furnace flame sensor is the standard solution for resolving short-cycling and "no flame detected" error codes.

• Precise Flame Detection: Engineered to provide accurate flame rectification, ensuring the control board receives a consistent microamp signal for continuous operation.
• OEM Compatibility: Specifically designed to replace Lennox 69W4301, LB-74940B, and 102431-02, facilitating a perfect fit in the mounting bracket.
• High-Temperature Durability: Features a robust Kanthal or stainless steel rod and ceramic insulation to maintain structural integrity under extreme heat.
• Enhanced System Safety: Prevents unburned gas flow by immediately signaling the gas valve to close if the flame is not sensed during the ignition window.
• Direct Field Replacement: Equipped with a standard 1/4-inch quick-connect terminal and single-hole mounting for rapid installation during service calls.

What are the signs of a failing Lennox 69W43 flame sensor?
Common indicators include the furnace shutting off 2-5 seconds after the burners ignite, repeated furnace ignition failure, and control board error codes for "low flame signal" or "flame rollout." Physical inspection often reveals heavy carbon buildup or oxidation on the rod.

Can I clean the 69W43 sensor instead of replacing it?
While cleaning with fine steel wool or an emery cloth can provide a temporary fix for dirty flame sensor symptoms, microscopic pitting in the metal rod eventually leads to signal instability. Replacing the component is the standard practice for long-term system reliability.

Is the 69W43 compatible with other brands besides Lennox?
Yes, this is an OEM part used across the Allied Air family, making it the correct furnace replacement part for many Armstrong, Ducane, Concord, and Magic-Pak gas furnaces.

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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.