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52W29 Lennox LB-74940A, Flame Sensor Kit, Straight Probe

52W29 Lennox LB-74940A, Flame Sensor Kit, Straight Probe

Low stock: 10 left

Regular price $45.24 USD
Regular price Sale price $45.24 USD
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Key Features & Specifications

  • Genuine Lennox OEM Flame Sensor

  • Ensures Safe Furnace Ignition & Operation

  • High-Temperature Resistant Build (2190°F)

  • Direct Replacement for P/N 31L71 & LB-74940A

  • Compatible with G40, G50, G60, G71 Series

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Specifications

Product Details and Key Specifications:

  • Part Number: 52W29
  • Manufacturer: Lennox (Genuine OEM)
  • Part Type: Flame Sensor Kit
  • Catalog Number: 52W29
  • Model/Part #: LB-74940A
  • Rod Length: 2.75" (2-3/4")
  • Total Length: Approx. 5.25"
  • Diameter: 0.114 in (Probe Diameter)
  • Termination: 1/4" Male Spade Quick Disconnect
  • Max Temperature: 2190°F
  • Gross Shipping Weight: 1.5 LB

description

Lennox P/N 52W29 (LB-74940A) – Genuine OEM Straight Flame Sensor Kit


The Lennox 52W29 (also known as Catalog Number 52W29 and Manufacturer Part Number LB-74940A) is a genuine OEM straight flame sensor designed for a wide range of Lennox, Allied, Armstrong, Concord, and Ducane gas furnaces. This critical safety component continuously monitors the presence of a flame within the combustion chamber. If the control board does not receive this signal, it safely shuts off the gas flow, preventing the buildup of unburned gas and maintaining system safety.

Being a Genuine OEM part from Lennox ensures optimal compatibility and reliability. Unlike universal alternatives, this sensor is built with high-temperature resistant materials (a rod capable of withstanding up to 2190°F) to the exact specifications required by the furnace's safety circuits. This precision fit and validated functionality are crucial for preventing nuisance shutdowns and ensuring dependable, long-term performance across compatible G40, G50, and G60 series furnaces.


Key Features and Function:

  • Accurate Flame Detection: Precisely monitors the burner flame signal to confirm successful ignition and continuous combustion.
  • Genuine OEM Reliability: Official part from Lennox, ensuring perfect fitment and validated functionality for compatible units.
  • Durable, High-Temp Construction: Built to withstand demanding combustion environments, operating in temperatures up to 2190°F.
  • Direct-Fit Design: Features a straight rod design and a standard 1/4" male spade terminal for easy, direct installation.


Product Details and Key Specifications:

  • Part Number: 52W29
  • Manufacturer: Lennox (Genuine OEM)
  • Part Type: Flame Sensor Kit
  • Catalog Number: 52W29
  • Model/Part #: LB-74940A
  • Rod Length: 2.75" (2-3/4")
  • Total Length: Approx. 5.25"
  • Diameter: 0.114 in (Probe Diameter)
  • Termination: 1/4" Male Spade Quick Disconnect
  • Max Temperature: 2190°F
  • Gross Shipping Weight: 1.5 LB


🛠️ HVAC Depot Pro Tip: Clean Before You Replace

The most frequent cause of a furnace fault code related to the flame sensor (symptoms include the furnace lighting and then shutting off quickly) is carbon buildup on the sensor rod. Before replacing the 52W29, always try cleaning the existing rod with fine steel wool or an emery cloth. This simple maintenance step often restores the proper micro-amp signal, potentially fixing the issue without needing a new part.


The 52W29 is a direct OEM replacement for the following part numbers:

  • OEM Numbers:

    52W29, 52W2901, 31L71, 31L7101, LB-74940A, LB47940A.
  • Cross-Refs:

    28PV41, FLS52W29.


Extensive Model Compatibility List:

Note: Use 'CTRL+F' to search for your specific model:

  • Lennox G40 Series:

    G40DF-24A/36A/36B/48B/48C (Various Revisions).
  • Lennox G41UF Series:

    G41UF-45, -70, -90, -110, -135 (Various Revisions).
  • Lennox G43UF Series:

    G43UF-45, -70, -90, -90H, -110, -110H, -135 (Various Revisions).
  • Lennox G50, G51 Series:

    G50DF-45/70/90/110/135 (and X variants).
  • Lennox G60, G61, G71 Series:

    G60UH-48B-090X (and various G61 & G71 models).

Specification

Refund policy

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Last Updated: June 2026

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We recommend using a trackable shipping service and purchasing shipping insurance for higher-value items.

Return Address

HVAC Parts & Equipment Depot
1135 E Plano Parkway, Suite 8
Plano, TX 75074
United States

Professional Installation Notice

Many HVAC products require installation by a licensed HVAC professional.

HVAC Parts & Equipment Depot is not responsible for damages resulting from improper installation, misuse, unauthorized modifications, or failure to follow manufacturer instructions.

Special Orders

Special-order products must be picked up within 30 days of purchase unless other arrangements have been approved.

Unclaimed special-order products may be returned to the manufacturer and may be subject to applicable restocking fees.

Contact Us

If you have questions regarding returns, refunds, or exchanges, please contact us:

HVAC Parts & Equipment Depot

Phone: (214) 734-5222
Email: support@tophvacparts.com

Michel & Siso are very knowledgeable and explain everything to where I could understand! Amazing experience! Thank you will always come here for any AC needs. Trustworthy and excellent customer service.

Celest G.
Verified Customer
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