Lennox 90H83 Flame Sensor

When you're dealing with a furnace that keeps cycling off after just a few seconds of ignition, the Lennox 90H83 Flame Sensor is often the culprit. This genuine HVAC OEM part is critical for the flame rectification process, converting the heat of the burner into a microamp signal that tells the ignition control board it’s safe to keep the gas valve open. Designed as a direct Lennox furnace replacement, the 90H83 features a 2.5-inch element length with a specific 90-degree offset to ensure it sits precisely in the path of the last burner’s flame. Over time, carbon buildup or cracks in the porcelain insulator can lead to signal loss, resulting in nuisance lockouts. This furnace flame rod replaces older part numbers including R39073B001 and T6-2092, and is compatible with various Lennox, Armstrong, and Ducane units. For a veteran tech, swapping this out is a standard fix to restore heating system reliability and maintain peak combustion efficiency. Skip the temporary cleaning and drop in a fresh Lennox 90H83 to ensure the sensor reads the proper 1.5 to 5.0 microamp signal consistently throughout the heating season.

• Precise Flame Detection: Engineered for accurate flame rectification to prevent unnecessary system shutdowns.
• OEM Compatibility: Exact replacement for Lennox, Allied, Armstrong, Concord, and Ducane gas-fired equipment.
• High-Temperature Durability: Constructed with a high-grade steel rod and robust porcelain insulator for long-term thermal resistance.
• Direct Fit: 90-degree bend and 2.5-inch rod length ensure perfect positioning within the burner assembly.

What are the symptoms of a bad Lennox 90H83?
The most common sign is the "short cycling" effect where the burners ignite for 2-5 seconds and then immediately shut off. This usually repeats several times before the control board goes into a hard lockout mode.

Can I just clean the sensor instead of replacing it?
While cleaning with a very light abrasive can temporarily restore signal, it often removes the protective coating on the rod, leading to faster carbon buildup. If the porcelain is cracked, cleaning will not work and the part must be replaced to prevent grounding issues.

How do I test if this sensor is the problem?
Measure the microamps (µA) by placing your multimeter in series with the flame sensor wire. A healthy Lennox system generally needs to see a reading above 1.0 µA; anything lower indicates a dirty or failing sensor.

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.