Description
The Lennox 20J91 is an OEM replacement flame sensor engineered to deliver precise and reliable flame detection in Lennox furnace systems. Designed as a direct factory-spec replacement, this sensor helps maintain safe and efficient furnace operation by accurately sensing the presence of a burner flame and signaling the control board to keep the gas valve open.
Why Replace Your Flame Sensor?
A worn or contaminated flame sensor is one of the most common causes of furnace short-cycling and no-heat calls. The sensor’s rod can accumulate oxidation over time, reducing its ability to conduct the microamp signal needed to verify flame. Replacing it with a genuine Lennox OEM part restores proper communication between the burner and the control board, preventing nuisance lockouts and unnecessary service calls.
Key Features
- Genuine Lennox OEM replacement — SKU 20J91
- Direct-fit design for compatible Lennox furnace models
- Ensures accurate flame rectification signal to the furnace control board
- Helps prevent furnace short-cycling and lockout faults
- Manufactured to Lennox factory specifications for reliable, long-term performance
- Supports safe furnace operation by confirming burner flame presence
Application
The Lennox 20J91 flame sensor is intended for use in compatible Lennox gas furnace systems. Always verify compatibility with your specific furnace model number before installation. Consult the furnace service manual or Lennox technical support for approved replacement guidance.
Installation Notes
- Disconnect power and shut off gas supply before servicing
- Handle sensor rod carefully — avoid touching with bare hands to prevent contamination
- Ensure secure electrical connection to the furnace control board harness
- Test furnace operation after installation to confirm proper flame sensing
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