Lennox 40L81 Flame Sensor – LB-94701A

OEM Part Number: LB-94701A
Catalog Number: 40L81
Brand: Lennox Genuine OEM
Product Type: Flame Sensor Kit

Common Symptoms of a Faulty Flame Sensor

A dirty or failing flame sensor can cause your furnace to shut down even though all other components appear to be working normally. Common symptoms include:

• Furnace ignites but shuts off after a few seconds.
• Burners light and then immediately go out.
• Furnace repeatedly tries to ignite.
• Lockout or ignition fault codes.
• No heat even though the inducer motor and igniter operate normally.
• Intermittent heating during cold weather.
• Furnace runs for one cycle but fails on the next call for heat.

During the winter months, these problems are common throughout Alberta, including Calgary, Edmonton, Red Deer, Lethbridge, Medicine Hat, Fort McMurray, Grande Prairie, Airdrie, Sherwood Park, and St. Albert, where furnaces often run continuously during extended cold periods.

In Ontario, homeowners in Toronto, Mississauga, Brampton, Vaughan, Markham, Richmond Hill, Oakville, Burlington, Hamilton, Ottawa, Kingston, Cornwall, Oshawa, Whitby, Ajax, Pickering, Barrie, and London frequently experience flame sensor issues after years of normal furnace operation or from carbon buildup on the sensor rod.

Compatible Lennox Furnace Models

The Lennox 40L81 Flame Sensor Kit is used on many Lennox furnaces equipped with the SureLight ignition system, including:

• G23 Series
• G26 Series
• G32 Series
• 90UGF Series