Find the letter in the middle of the serial number. The first two numbers after it are the week of manufacture, and the third and fourth numbers after the letter are the year of manufacture. The month and year of manufacture is also indicated at the upper right of the data plate. So the “M3004” in the serial number below means it was manufactured in the 30th week of 2004, and the “MFD. 07/04” confirms it. For the age of another brand or manufacturer, go to our blog post How do I determine the age of my air conditioner?

    To find the size of your Ruud system, go to How many tons is my Ruud air conditioner or heat pump?

    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? 

• 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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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.