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The genuine OEM Lennox 69W43 flame sensor is a critical safety device that verifies a flame is actually present after your furnace attempts ignition. Using flame rectification, it sends a small signal to the control board confirming the burners have lit — if no flame is detected, the board shuts off the gas valve to prevent unburned fuel from accumulating.
Common failure symptoms: A dirty or failing 69W43 is one of the most common causes of short cycling — the furnace lights, runs for a few seconds, then shuts down, repeating the sequence until it locks out. You may also see no heat, intermittent operation, or repeated ignition-lockout faults on the control board.
Why OEM matters: Flame sensors depend on precise placement, rod material, and electrical characteristics to generate a reliable microamp signal. The factory-original Lennox 69W43 is built to those exact specifications, ensuring dependable flame detection and full compatibility with your ignition control. For a component central to combustion safety, OEM is the right call.