The 8th digit of the serial number, which will be a letter (and typically the next to last digit) denotes the year of manufacture for units manufactured from the 1980s to the early 1990s: 

A = 1980                   I = (not used) 

B = 1981                   J = 1988

C = 1982                   K = 1989

D = 1983                   L = 1990

E = 1984                    M = 1991

F = 1985                    N = 1992

G = 1986                   

H = 1987

An example, shown below, is: A 10322EDB

The next to last letter indicates it was manufactured in 1983. Here’s an example of the nameplate from that era.

Beginning in the early 1990s the third and fourth numbers are the year of manufacture, followed by a single letter and more numbers, so the the condenser unit with the serial number below was manufactured in 2007.

There was also a format used for a while that placed the year of manufacture at the 7th and 8th digits of the 10-digit sequence that is all numbers. So, for example, serial number 5258470429 would indicate a 2004 year of manufacture. To determine the size of your air conditioner, go our blog post How many tons is my Armstrong Air heat pump or air conditioner?

    For the age of another brand or manufacturer, go to our blog post How do I determine the age of my air conditioner?

    To determine other key specs of your HVAC system, see one of these other blog posts: 

• How can I find out the SEER of my air conditioner?

• How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

• How can I find out the size of my air conditioner? 

    To find the age of other home components, go to How can I find out the age of a roof? and How do I determine the age of an electrical panel? and How do I determine the age of my water heater? For life expectancies, visit What is the average life expectancy of the components of a house? 

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  To learn more about heating and air conditioning systems, see these other blog posts: 

• My air conditioner won't turn on. What's wrong?  

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.