OEM Lennox Ignitor & Flame Sensor Assembly — 73K38

The genuine OEM Lennox 73K38 is a combined ignitor and flame sensor assembly that manages the ignition sequence in your Lennox gas furnace. The ignitor heats up to light the burners on a call for heat, while the integrated flame sensor confirms that a flame is present and signals the control board to keep the gas valve open — a critical safety function that shuts off gas if no flame is detected.

Common failure symptoms include no heat or a furnace that ignites then shuts down after a few seconds, repeated short-cycling on the flame-sense circuit, a cracked or visibly worn ignitor element, or a furnace that locks out after several failed ignition attempts. A dirty, oxidized, or aged flame sensor is one of the most frequent causes of intermittent no-heat calls.

Why OEM matters: The 73K38 assembly is engineered to the exact resistance, mounting position, and flame-rod characteristics Lennox specifies, ensuring reliable ignition and accurate flame verification. Aftermarket substitutes can misread flame current or fail to seat correctly, leading to nuisance lockouts and unsafe operation. Installing the OEM assembly restores dependable, safe heating and protects your furnace's control system.