For York systems manufactured from October 2004 to the present, the first and third characters in the serial number will be letters, and the second and fourth characters will be numbers that indicate the year of manufacture. So, for example, the serial number below beginning with “W1D5” indicates that the condenser was manufactured in 2015.

    And here’s an example from a York furnace manufactured in 2009.

    An earlier serial number system, that was used until October 2004, has a sequence of four letters followed by a string of  six numbers. The third letter indicates the year of manufacture but, because the letter series repeated every 21 years, some letters will require you to look at the condition of the system or find the year of any industry standard referenced in the fine print of the data plate to determine which of the two years that used the same letter it is.

A = 1971 or 1992     B = 1972 or 1993  
C = 1973 or 1994     D = 1974 or 1995
E = 1975 or 1996     F = 1976 or 1997
G = 1977 or 1998     H = 1978 or 1999
J = 1979 or 2000     K = 1980 or 2001
L = 1981 or 2002     M = 1982 or 2003
N = 1983 or 2004  P = 1984  R = 1985
S = 1986    T = 1987    V - 1988
W = 1989    X = 1990   Y = 1992

    So WDHP875237 would be either 1978 or 1999. And here’s an example below that could be 1980 or 2001 but, but we also knew that the house was built in 2001—so it is the original system.

    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 the size of a York system in tons, see our blog post How can I tell the size in tons of a York air conditioner or heat pump from the model number? 

    And to figure out what all the other numbers listed on the condenser data plate mean, go to our blog post How do I understand the air conditioner or heat pump condenser label (data plate)?    

    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?  

    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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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at amazon.com for $19.95.
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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? 

• Does an old air conditioner use more electricity as it ages? 

• 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.