Furnace and AC age by serial number
Pick the brand, type the serial, see when the unit was made.
Serial formats by brand
Most manufacturers don't publish these formats. Each rule below is written from the structure of the serial and checked against U.S. government recall records where one exists. The examples are made up, except where a CPSC recall supplies the prefix. Mitsubishi readings list every year ending in the digit within the last 30 years. Units older than 30 years are possible but not listed.
Carrier / Bryant / Payne / Day & Night
- week then year, a plant letter, 5 digits (4 digits, a letter, 5 digits). Confidence: Medium.
Example 2318E12345. Characters 1 to 2, 23, are the week. Characters 3 to 4, 18, are the year. Character 5, E, is the plant.: 23 = week 23, 18 = 2018, E = plant: around June 2018. Sources: R1, R2, R3
Trane / American Standard / RunTru / Ameristar
- year, week and day code first (10 characters, the first 5 digits). Confidence: High.
Example 1630412345. Characters 1 to 2, 16, are the year. Characters 3 to 4, 30, are the week. Character 5, 4, is the day code.: 16 = 2016, 30 = week 30, 4 = day code: around July 2016. Sources: G3, R1, R2 - one-digit year then week (2002-2009) (9 characters, the first 3 digits). Confidence: Medium.
Example 523123456. Character 1, 5, is the year digit. Characters 2 to 3, 23, are the week.: 5 = 2005, 23 = week 23: around June 2005. Sources: R1, R2
Lennox
- plant, year, month letter (4 digits, a month letter, 5 digits). Confidence: High.
Example 5609H12345. Characters 1 to 2, 56, are the plant. Characters 3 to 4, 09, are the year. Character 5, H, is the month letter.: 56 = plant, 09 = 2009, H = August: August 2009. Sources: G4, R1, R2 - older 9-character format (1970s to 1990s) (a letter, 5 digits, 3 letters). Confidence: Low.
Example A79123BHC. Character 1, A, is the plant. Characters 2 to 3, 79, are the year. Character 8, H, is the month letter.: A = plant, 79 = 1979, H (character 8) = August: August 1979. Sources: R1
Goodman / Amana / Daikin (Goodman-built)
- 10 digits, year then month (10 digits). Confidence: High.
Example 1609123456. Characters 1 to 2, 16, are the year. Characters 3 to 4, 09, are the month.: 16 = 2016, 09 = September: September 2016. Sources: G1, G2, R1, R2
Rheem / Ruud / Weatherking
- plant letter in the middle, then week and year (10-15 characters, with F, G, M, N or W after character 1 followed by 4 digits). Confidence: Medium.
Example RAM520612345. Character 3, M, is the plant. Characters 4 to 5, 52, are the week. Characters 6 to 7, 06, are the year.: M = plant, 52 = week 52, 06 = 2006: around December 2006. Sources: G5, R1, R2 - plant letter first, then week and year (a letter, 9 digits). Confidence: Medium.
Example F361912345. Character 1, F, is the plant. Characters 2 to 3, 36, are the week. Characters 4 to 5, 19, are the year.: F = plant, 36 = week 36, 19 = 2019: around September 2019. Sources: R2
York / Luxaire / Coleman (Johnson Controls brands)
- plant letter, year tens digit, month letter, year units digit (a letter, a digit, a letter, 7 digits). Confidence: Medium.
Example N1E6123456. Character 1, N, is the plant. Character 2, 1, is the tens digit of the year. Character 3, E, is the month letter. Character 4, 6, is the units digit of the year.: N = plant, 1 and 6 = 2016, E = May: May 2016. Sources: R2, R1 - 4 letters (plant, month, year, product), then 6 digits (4 letters, 6 digits). Confidence: Medium (Low for the 1971-1991 cycle).
Example WFKM123456. Character 1, W, is the plant. Character 2, F, is the month letter. Character 3, K, is the year letter.: W = plant, F = June, K = 2001 (or 1980 in the older cycle): June 2001. Sources: G6, R2, R3
Mitsubishi Electric
- year digit, then month code (a digit, a month code (1-9, X, Y or Z), 4 or more characters). Confidence: Medium.
Example 5X0214. Character 1, 5, is the year digit. Character 2, X, is the month code.: 5 = a year ending in 5, X = October: October 2025, 2015 or 2005. Sources: M1, R1
Bosch
- 3-character date code at characters 5 to 7 (not decoded) (7 or more characters). Not decoded: the code table was not obtained.
Example 123456789012. Characters 5 to 7, 567, are the date code (not decoded).: 567 = date code (Bosch table not obtained, so not decoded). Sources: B1, R1
York, Luxaire and Coleman month letters: the references disagree after August (one key runs A-M without I, the other A-H and K-N without I or J), so the tool shows both readings for K, L and M and marks J and N as Low.
Questions
How do I tell how old my furnace or AC is?
Find the serial number on the data plate and decode it by the brand's format. Every brand encodes the date differently, and many plates also print a manufacture date. If yours does, that date wins. The serial gives the manufacture date. The install date is on the invoice or the permit.
Why does the tool show two or three possible dates?
Some formats store only the last digit of the year (Mitsubishi, Trane 2002-2009) or a repeating year letter (older York, Luxaire and Coleman). The plate settles it: R-22 refrigerant means made before 2010 (EPA), and SEER2 ratings mean 2022 or later.
A salesperson says my unit is from the 1980s. How can I check?
Look at the characters this tool highlights and the rule it names. You can check the reading yourself on the plate, and if the plate shows SEER2 or R-410A, a 1980s date is unlikely.
Do I have to register my new furnace or AC for the warranty?
Most brands require registration within 60 or 90 days of installation for their longer parts warranty: Carrier, Bryant, Payne, York and Mitsubishi allow 90 days; Trane, Lennox, Goodman and Rheem allow 60. In Florida (installs from July 2024) and Georgia (from January 2026), state law says registration can't be required.
My unit is 20 years old and still works. Should I replace it?
Not because of age alone. DOE uses about 21 years for a gas furnace and 15-25 for heat pumps and central AC as typical lives, and ENERGY STAR suggests planning ahead past 10 years (AC, heat pump) or 15 (furnace). Use the repair-or-replace calculator when a repair quote comes in.