The Location of a Lennox Serial Number and How To Read It

Posted by: Mas Broto
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Lennox serial number is attached on the data plate that provides essential information regarding the unit. Serial number indicating the age of the unit and where it was manufactured. Read on to know more about Lennox serial number, where to find and how to decode it.

Serial number is important to identify the age of the unit. You can identify the Lennox furnace age by serial number. But first, you must find the location and be able to read and decode the Lennox nomenclature.

When deciding whether to repair or replace your HVAC unit, it’s a good idea to check out the age of the unit first. Lennox HVAC units have a beneficial life up-to 20 years in general. If your unit is getting close to that age range, you may want to consider to replace.

Lennox Serial Number Location

The Lennox serial number should be on a little sticker that is attached on the back of the unit inside the main case. The sticker is actually attached to the circuit board inside.

Serial Number Location on Lennox Furnace

You can find the Lennox serial numbers and model numbers of your furnace by removing the top-front support panel. Looking to the left side of the in house cabinet or the top of the blower deck. Find the series of numbers and letter that follow the word “Serial” on that data plate.

Serial Number Location on Lennox AC and Heat Pump

Lennox serial number of AC and Heat Pump unit can be found on the side of the air conditioner housing of the outdoor unit. Find a metal nameplate attached in the backside of the cabinet.

How to Read Lennox Serial Number

Now that you know the location of Lennox serial number, its time to decode it. New Lennox serial numbers usually contain 4 numbers followed by a letter. The first 2 numbers stand for the factory location, the second 2 numbers are the year and the following letter is the month.

Month Index


How old is my Lennox HVAC unit?

The date of the manufacture or age of Lennox® HVAC unit can be determined from the serial number located on the data plate. Lennox have a different styles of serial number.

Example Lennox serial number styles:

#5120L13681 (Ten (10) character Serial number begins with four (4) numerical digits followed by one (1) letter and ends with five (5) numerical digits.)

  • Year of manufacture is in the 3rd-4th character
  • Month of manufacture is in the 5th character

#C89274AAC (Nine (9) character Serial number begins with one (1) letter digit followed by five (5) numerical digits and ends with three (3) letter digits.)

  • Year of manufacture is in the 1st-2nd character
  • Month of manufacture is in the 3rd character

#12D67 JA098 (Ten (10) character Serial number begins with two (2) numerical digits followed by a letter and two (2) more numerical digits – a space – and ends with two (2) letters followed by three (3) numerical digits)

  • Day of manufacture is in the 1st-2nd character
  • Month of manufacture is the 3rd character
  • Year of manufacture is the 4th-5th character

#2120720614 (Ten (10) digit character numerical Serial number)

  • Year of manufacture is in the 7th-8th character
  • Work Week of manufacture is in the 9th-10th character

Index of Lennox Manufacturer Locations

51: Columbus, Ohio
53: Des Moines, Iowa
54: Ft. Worth, Texas
55: Stone Mountain, Georgia
56: Stuttgart, Arkansas
58: Marshalltown, Iowa
63: Toronto, Ontario


Finding the age of your Lennox HVAC system is important to recognizing the estimated life left. It help many homeowners make a decision whether to repair or replace it. If you still unsure about Lennox serial number lookup and difficult to read, call a trained HVAC technician to tell you when the unit was installed, how long it’s been operating and it’s time to repair or replace it.

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Mas Broto
Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.