How old is my American Standard furnace or AC?

By Dana Whitlock. Updated October 2026. Widely documented.

A letter at the front of an American Standard serial means the unit was built in 2001 or earlier. The serial comes in three styles, and each one marks an era. Ten characters starting with two digits: 2010 or later, year first, then week. Nine characters starting with one digit: 2002 through 2009. Nine characters led by a letter: 1983 through 2001.

These are Trane's formats, since both brands roll out of the same factories, and recall notices and inspector references agree on them. Many American Standard plates also print a manufacture date in words or numbers. When one is there, it beats anything you decode.

Where to find the label on a American Standard furnace

Indoors, find the white label on a side wall of the furnace. On many units you need the front door off to see it. Set the thermostat to off and flip the furnace's service switch first, then lift the door and read the label from outside the cabinet with a flashlight. Outside, the condenser or heat pump has its plate on the cabinet, often near the refrigerant connections. If the label is behind anything held with screws, a licensed HVAC technician can read it during a regular service visit.

How to read the code

For the modern ten-character style, split off four digits: YY then WW. A serial beginning 1447 is week 47 of 2014, late November, which lines up with a 2015 CPSC recall of accessory heaters made from November 2014. For the 2002 to 2009 style, the first digit is the year's final digit and the next two are the week; a utility contractor reference reads 7165RHAIG as the 16th week of 2007. For the letter style, the opening letter is the year and the two digits after it are the week. B50632891 is week 50 of 1987, which is December 1987. Sample letter codes: W is 1983, S is 1986, B is 1987, E is 1990, K is 1995, N is 1998, R is 2000 and Z is 2001.

Real serials in this code

When the format changed

Two traps catch people. First, length. A nine-character code starting 5 means 2005. The single-digit era ended in 2009, so it can't be 2015. Second, the year letters do not follow the alphabet neatly. W, X and Y come first for 1983 to 1985, S stands for 1986, B through H then march forward from 1987, and Z closes out 2001. The letters I, O and Q are never used. Some references start the two-digit era in 2009 instead of 2010. The weeks are fiscal weeks, so the first and last weeks of a year can spill into the next or previous calendar year. American Standard's warranty and registration site can help confirm a reading.

Who makes American Standard

American Standard heating and cooling equipment is made by the same company as Trane. Back in 2005, American Standard Companies was the parent behind both brands, and the CPSC's 2017 furnace recall listed Trane, American Standard and Ameristar furnaces under Trane U.S. Inc. All three use identical serial formats. American Standard is sold through independent HVAC dealers. The old parent company sold its bath and kitchen division in 2007 and renamed itself Trane, which is why the plumbing brand and the furnace brand now go separate ways.

How sure is this?

Widely documented. American Standard doesn't publish this code; it comes from recall notices, service literature and inspector references. We tested the trane rules against 17 serials, 7 of them with a date known from a recall notice, a printed label date or the maker. None decoded to a wrong year; codes whose year mark repeats show every possible reading. Always confirm with American Standard's serial lookup before you spend money on the answer.

Quick notes

• Scan the label for a printed date first. American Standard prints one often enough that you may not need to decode anything.
• Nine characters with a leading digit means 2002 to 2009; do not add ten years.
• A leading letter means pre-2002, and that unit is now more than two decades old.
• If the American Standard furnace and outdoor unit decode to different eras, they were likely installed at different times.