OEM Lennox Flame Sensor — 39F95

The genuine OEM Lennox 39F95 flame sensor is a critical safety component in your Lennox gas furnace. Using the principle of flame rectification, it confirms that a flame is actually present after the igniter fires. If the control board doesn't detect a healthy flame signal within seconds, it shuts off the gas valve to prevent unburned gas from accumulating — protecting your home from a dangerous condition.

Common failure symptoms: A dirty, corroded, or failed 39F95 flame sensor is one of the most common causes of a furnace that lights briefly then shuts down. Watch for short-cycling, the burner igniting and going out after a few seconds, no heat despite the igniter glowing, or repeated ignition lockouts. Oxidation buildup on the sensor rod weakens the microamp flame signal over time.

Why OEM matters: The flame sensor's rod material, length, and mounting position are precisely calibrated to your Lennox burner assembly. The factory 39F95 ensures a reliable flame-current reading and correct safety response. A mismatched aftermarket sensor can cause nuisance lockouts or fail to trip the safety shutoff — reasons to trust the OEM part for both performance and safety.