As a homeowner, your furnace is one of the appliances that fits the mantra: “out of sight, out of mind”. Yet, it’s critical for keeping your home comfortable when outdoor temperatures turn colder. While knowing the age of your furnace may help you budget for the cost of replacement, it’s more often used to determine an appropriate servicing or maintenance plan for a system that is experiencing issues, whether it’s not working efficiently or at all.

Determining the Age of Your Appliance

The first step in trying to figure out the age of your furnace is to look for a removable door or service panel on the outside of the appliance. Once you remove the door, you should be able to find a label or tag listing the serial number.  It may also show the actual manufacturer’s date. However, finding the age of your furnace may vary slightly depending on the manufacturer. 

Finding the Age of a Trane Furnace

First, find the tag that contains the serial number. On newer Trane furnaces, the serial number label is located on the right or left panel of the furnace. Beginning around 1982, the date of manufacture was typically stamped onto the panel. For older units, the year is a single digit number followed by a letter in the serial number. For example: 1Cxxxx could be March 1971, 81, 91, 01. For more detailed instructions, refer to this guide.

Finding the Age of a Lennox Furnace

Find the serial number inside the service panel, as shown in the video. Use the serial number to determine the manufactured date. Some furnaces actually have a separate sticker with the year specified.

Before 1974, the first 2 digits indicated the year. For example: 732xxx = February 1973.

On newer units (1974 and beyond) the 3rd and 4th digit represent the year. The 5th digit should be a letter and represents the month (A thru M minus I). For example: 5898G 07568 would be from July (G) of 1998.

Finding the Age of a Goodman Furnace

The serial number can be found on the tag inside the service panel.  

Once you have the serial number, you can determine the manufacture date. The first two digits of the serial number are the year, while  digits three and four represent the month of manufacture.

Finding the Age of a Rheem Furnace

Find the serial number for your Rheem furnace and enter it into their online portal to determine the date it was manufactured.

To Repair or Replace

It’s important to be aware of how old your furnace is, but age is not the only indication that it may need to be replaced.  The average lifespan is between 15 to 20 years, so you need to be aware of any abnormal functions, sounds and smells.  

If you are experiencing any of the following issues you should call an HVAC technician to see if your unit can be repaired or needs to be replaced.

  • The most obvious problem would be that your home is not being heated properly, often it’s the motor in the blower fan, heat exchanger or pilot light.
  • HVAC systems usually make noise but if you start hearing pops or squeaks it may indicate something has come loose.
  • An increase in your heating bill is also a good indication that your furnace is no longer efficient enough to heat your home as quickly as it used to.
  • Unless you have an all electric furnace, check your pilot light – it should always be blue.  A yellow pilot light is not only a warning sign that the furnace needs repairs, it could be leaking carbon monoxide.  If your pilot light is yellow or you notice excessive condensation, rust or a rotten egg smell, shut off your furnace immediately and call an HVAC technician.
  • Soot and rust around your registers is usually caused by an excess of CO2 which can harm floors, walls and wooden surfaces.  This issue can also cause dry eyes and scratchy throats.
  • You should also call for service, obviously, if your furnace keeps shutting down.

It’s important to keep your HVAC system running efficiently and safely.  Do this by changing the filters regularly and having a professional technician service it yearly.  If this is done, any problems should be determined easily.  But, if you haven’t had this done, please be aware of any of the conditions listed above.