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The genuine OEM Lennox 90H83 flame sensor confirms the presence of a flame during furnace ignition, using flame rectification to signal the control board that it's safe to keep the gas valve open. This small but critical safety component protects your home by shutting off gas flow whenever combustion isn't verified in your Lennox furnace.
A dirty or failing flame sensor is one of the most common causes of furnace problems: the burners light and then shut off after a few seconds, the furnace short-cycles repeatedly, or it locks out entirely and won't produce sustained heat. A cracked porcelain insulator, carbon buildup, or a corroded rod all weaken the micro-amp signal the board needs to see.
Choosing the OEM Lennox 90H83 ensures the correct rod length, insulator, and mounting position so the sensor sits properly in the flame and reads an accurate signal. Off-brand sensors can misread flame current and cause nuisance lockouts or unsafe operation. The factory part restores dependable ignition and maintains warranty coverage.