Residential Furnaces, Heat Pumps & Air Conditioners
How Old Is My Lennox?
Type the serial number from the rating label on your Lennox furnace, AC or heat pump to see when it was made and how much of its typical 15-year life is left.
Try an example:
Where to find the serial number on a Lennox
On an outdoor AC or heat pump, the rating plate is on the side of the cabinet near the copper lines. On a furnace, remove the upper front door; the label is on the inside wall or the door itself.
Tip: in a dark basement or closet, take a photo of the label with your phone's flash on and zoom in on the photo.
How to read a Lennox serial number
Plant + year + month letter (10 characters)
Used 1973–today
Digits 1-2 are the factory. Digits 3-4 are the year. The 5th character is the month letter (A = January ... H = August, J = September ... M = December; I is skipped). 5818C = March 2018.
Example: 5818C12345 → March 2018
Common replacement parts for Lennox
Always match the part to the model number on your rating label, and have gas or refrigerant work done by a licensed technician.
- Lennox 70W16 Flame Sensor ReplacementCheck price on Amazon
- Lennox X6672 Healthy Climate Carbon Clean MERV 16 Filter (16x25x5)Check price on Amazon
Common questions about Lennox equipment
Where is the model and serial label on a Lennox gas furnace?
Remove the upper front access door of the furnace; the white diagnostic specification label is located on the inside left or right steel casing wall next to the burner assembly.
What is the warranty period on a Lennox heat exchanger?
Lennox standard furnaces typically include a 20-year or lifetime limited warranty on the primary heat exchanger if registered within 60 days of installation.
How long does a Lennox furnace, AC or heat pump last?
About 15 years on average. Units that get yearly maintenance often last longer; units in hard-water areas, coastal air or unconditioned spaces often fail sooner.
Is the serial number the same as the model number?
No. The model number describes the product line, size and options. The serial number identifies your exact unit and contains the manufacture date. Both are printed on the same rating label.
How accurate is this age estimate?
The date comes from the published serial number formats for each brand. It is the factory date, not the installation date, and some formats repeat every 10 or 20 years. If the label shows a printed MFG. DATE, that date wins.