Lennox 17J56 Flame Sensor

The Lennox 17J56 Flame Sensor is a critical OEM replacement part engineered for precise flame rectification in residential and light commercial Lennox furnace units. Also identified by part number 17J5601 and catalog number T6-2108, this flame sensing rod utilizes a high-grade Kanthal sensor and a glazed L-5 steatite insulator to ensure robust electrical continuity even under extreme thermal stress. In a standard sequence of operation, the integrated control board sends a 110V-120V AC signal to this probe; once the burner ignites, the flame acts as a conductor to ground, rectifying the signal to a DC microamp current—typically requiring at least 1.7 to 5.0 microamps (µA) for the gas valve to remain energized. If your system exhibits short-cycling or fails to prove flame after ignition, replacing this HVAC flame sensor is a standard diagnostic step to prevent ignition lockout and ensure safe, consistent burner performance.

Key Benefits:

• OEM Compatibility: This genuine Lennox part is a direct replacement for 17J5601 and T6-2108, ensuring exact fitment in Lennox unit heaters and furnaces.
• Enhanced Durability: Features a high-quality silicon carbide or specialized metal alloy rod and nickel-plated steel terminal for corrosion resistance in the combustion chamber.
• System Reliability: Accurate flame rectification prevents nuisance shutdowns and ensures the control board receives a high-fidelity microamp signal.
• Technical Precision: Designed with a 0.114-inch diameter rod and a 3.05-inch width, maintaining the specific spatial orientation required for the burner flame envelope.

Common Questions:

What are the symptoms of a bad Lennox 17J56 flame sensor?
The most common symptom is a furnace that ignites for 2 to 5 seconds and then immediately cycles off. This usually indicates the rod is dirty or the ceramic insulator is cracked, preventing the signal from reaching the control board.

Can I clean the 17J56 flame sensor instead of replacing it?
While light carbon buildup can often be removed using a fine emery cloth or 220-grit sandpaper, any visible cracks in the porcelain insulator or significant thinning of the metal rod requires immediate replacement to ensure system safety.

What microamp reading should I see on my multimeter?
On most Lennox units, a healthy 17J56 sensor should generate between 2.0 and 6.0 microamps DC. Anything consistently below 1.0 microamp will typically trigger a lockout code on the integrated furnace control board.

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.