HVAC Reference Tool
HVAC Serial Number Lookup
Pick the brand, paste the serial number, and get the manufacture date with a character-by-character explanation, the unit's age, the refrigerant era it was built in, and what all of that means for warranty and the repair-or-replace call.
Paste the serial and we run every documented format at once. Where two brands read the same digits as different years, you will see both readings instead of one guess.
Starting the decoder. The serial formats further down this page are already loaded, so you can read yours off them now.
Decode schemes compiled from secondary home-inspection and parts references. 8 of the 38 decode rules rest on a single secondary reference. Where two agree, that is weaker evidence than it looks: secondary references copy one another, and agreement between two is not a manufacturer document being read. Be clear on what that is worth: 33 of the 38 decode rules here rest on reference compilations rather than on a document from the company that built the unit. Formats whose documentation conflicts are declined rather than guessed. The date stamped or printed on the data plate, where present, always outranks a serial decode.
How Serial Number Formats Work, by Brand Family
HVAC brands cluster into manufacturing families that share plants, data plates, and serial formats. Learn one family's rule and you can date the brands in it, with the one exception the note under the table names. The rightmost column shows the low-GWP A2L refrigerant each family adopted for equipment manufactured from 2025 on.
| Brand family | Serial format | Where the year is | 2025+ refrigerant |
|---|---|---|---|
| Carrier, Bryant, Payne, Day & Night | 4 digits + letter + 4-6 digits | Digits 3-4 (digits 1-2 are the week) | R-454B (Puron Advance) |
| Heil, Tempstar, Comfortmaker, Arcoaire, KeepRite, Airquest | Plant letter (sometimes omitted) + 8-10 digits | First digit pair after the letter (year comes first, the reverse of Carrier) | R-454B |
| Trane, American Standard, Ameristar | 9 chars (1983-2009) or 10+ chars (2010+) | Leading letter (1983-2001), leading digit (2002-09), digits 1-2 (2010+) | R-454B |
| Goodman, Amana, Daikin unitary | 10 digits | Digits 1-2 (digits 3-4 are the month) | R-32 |
| Lennox | 4 digits + month letter + 5 or 6 digits | Digits 3-4 (the letter is the month) | R-454B ducted, R-32 ductless |
| Armstrong Air, AirEase, Ducane, Concord | 4 digits + month letter + 5 digits | Digits 3-4 | R-454B |
| Rheem, Ruud, WeatherKing, Sure Comfort | Letter + 9 digits | Digits 4-5 (digits 2-3 are the week) | R-454B |
| York, Luxaire, Coleman, Fraser-Johnston, Guardian | Letter-digit-letter-digit + 6 digits | The two digits read together (second letter is the month) | R-454B |
| Intertherm, Miller, Gibson, Frigidaire, Maytag + Nortek brands | 12 or 13 characters | Characters 4-5 (6-7 are the month) | R-454B |
| Mitsubishi Electric | 9 characters | First digit = last digit of the year (decade from refrigerant) | R-454B |
| LG | Digit + 2 digits + sequence | First digit = last digit of the year (digits 2-3 are the month) | R-32 |
| Samsung | 10-11 or 15 characters | Year letter at position 4 or 8 (chart verified through 2018) | R-32 |
| Gree; MrCool (Gree-built) | Digits-first serials | Digits 3-4 (digits 1-2 are the week) | R-32 Gree, R-454B MrCool |
| Fujitsu, Senville, Pioneer | Sequential; no date encoded | Use the stamped date code or MFG DATE field on the unit | R-32 (Fujitsu) |
The nastiest trap in this table: Carrier-family serials are week-first (4006A = week 40 of 2006) while the ICP brands owned by the same corporation are year-first (4006A on a Heil would be week 6 of 2040, which is impossible, or year 2040, also impossible; but 9414B reads as 1994 week 14 on a Tempstar and week 94 of 2014, invalid, on a Carrier). Both readings exist only where each pair is at once a valid week and a year this tool can resolve. On every brand but one the nameplate settles it. Day & Night is the exception: it was a Carrier BDP brand and later an ICP brand, so it carries both layouts and its own nameplate cannot choose between them. This tool shows every valid reading, and the MFG DATE field on the data plate, where present, has the final say.
Serial Number Lookup by Brand
Open the dedicated decoder page for your brand, with its exact serial format, refrigerant timeline, and warranty context.
Nortek / Nordyne family
Allied Air family
Trane family
Janitrol (legacy)
Daikin
Lennox
Mitsubishi Electric
LG
Samsung
Gree
Midea
MrCool
Bosch
Bard
Friedrich
Worked Examples
Carrier 4006A17330
Four digits, a letter, five digits: the dominant Carrier-family style since about 1980. Digits 1-2 are the week (40), digits 3-4 the year (06), the letter is a plant code, and the rest is the production sequence. Week 40 of 2006 lands in early October. A 2006 Carrier sits in the Puron transition window (1996-2009) when both R-22 and R-410A lines were sold, so the nameplate refrigerant field decides which one this unit holds. At roughly 20 years old in 2026, it is at the end of typical service life.
Trane R1742DWBF
Nine characters starting with a letter: the 1983-2001 Trane style. The leading R maps to 2000 in Trane's year-letter table, and digits 2-3 are the week (17), so this unit was built in week 17 of 2000, late April. Two letters in that table sit out of alphabetical order: S is 1986 and Z is 2001. That is deliberate rather than a transcription slip, and a chart that puts those two letters in alphabetical order gives a different year for both. A 2000 Trane is R-22 era equipment, which makes any refrigerant-circuit repair in 2026 a replacement conversation.
Goodman 9704011000
Ten digits, no letters: the Goodman family style used since at least 1997, shared by Amana and Goodman-built Daikin unitary equipment. Digits 1-2 are the year (97), digits 3-4 the month (04): April 1997. The month slice must land in 01-12, which is how the decoder rejects wrong readings of this format. A 1997 Goodman is nearly 30 years old and long past service life.
York W1G7123456
Letter, digit, letter, digit, then six digits: the York/Johnson Controls style since October 2004, shared by Luxaire, Coleman, Fraser-Johnston, and Guardian. The oddity is that the year digits are split: position 2 (1) and position 4 (7) read together as 17, so 2017. The second letter is the month: G is July (I and J are skipped). The leading W is the Wichita, Kansas plant. A 2017 York is mid-life R-410A equipment where repair usually still wins.
Rheem W291013412
A letter then nine digits: the Rheem family style, shared by Ruud, WeatherKing, and Sure Comfort. Rheem encodes week and year, never a month: positions 2-3 are the week (29) and positions 4-5 the year (10), so week 29 of 2010, mid-July. That is the first model year of the R-410A mandate. The same decode covers Ruud serials letter for letter.
Why Honest Decoders Show Multiple Dates
Serial formats were designed for factories, not for lookups two decades later, and some genuinely cannot be pinned to one date. York's 1971-2004 year letters repeat every 21 years, so YHFM321456 is August of 1976 or 1997. Mitsubishi and LG encode only the last digit of the year, leaving the decade to the refrigerant or model generation. Rheem's digits-first style has two published readings that disagree on whether the leading pair is a week or a month (the year is certain either way). This tool's rule for all of these: run every documented reading, discard the ones that fail validity checks (weeks over 53, months over 12, years in the future), and rank what survives instead of presenting a coin flip as a fact. Formats whose documentation is outright contradictory, like the 22-digit Midea and MrCool serials, are declined with an explanation rather than guessed.
The rules are also checked against the outside world. 241 serial numbers beside which someone other than us published a date have been read, drawn from 47 separate documents published by 7 bodies: a federal regulator, five public bodies and one surplus marketplace. 203 of them produced a dated reading, against 15 of the 38 formats this decoder documents; 38 produced no reading at all under this tool's formats. For 12 of the 203, the published year and this tool's reading disagree. These are the rows read in from those documents so far; more rows from the same documents are still being read in. Where someone outside this tool wrote down a different year for a unit, that year is shown here rather than dropped. It is that publisher's record for the unit, and a schedule or a listing can carry a replacement, system or lot year rather than the build year. The MFG DATE on the unit's data plate is the build date. The documents behind the checks are listed in the source receipt below.
Frequently Asked Questions
How do I tell how old my AC or furnace is from the serial number?
Almost every major brand encodes the manufacture date in the serial number, but the position varies by brand family. On Carrier, Bryant, and Payne the first four digits are week then year (4006A = week 40 of 2006). On Goodman and Amana the first four digits are year then month (9704 = April 1997). On Trane, a leading letter maps to 1983-2001 and leading digits to 2002 and later. On Rheem and Ruud the week and year follow the leading letter. Pick your brand in the decoder above and it applies the right rule, including the ambiguous cases where two readings are possible.
Where is the serial number on an HVAC unit?
On an outdoor condenser or heat pump, the data plate is a metal or foil sticker on the side panel, usually near the refrigerant service valves. On a gas furnace, it is inside the cabinet: remove the front door and look on the blower housing or the inner side wall. On mini splits, check the right side or underside of the indoor head and the side panel of the outdoor unit. The serial is the one labeled S/N or SERIAL.
Is my unit still under warranty?
Most major brands follow the same structure: about 10 years of parts coverage if the unit was registered within 60 to 90 days of installation, and 5 years if it was not. Trane, Goodman, Lennox, Allied, and Rheem use a 60-day registration window; Carrier, York, and the ICP brands use 90 days. Daikin is the outlier at 12 years parts plus 6-year unit replacement when registered. Decode the age above, then run the serial through the manufacturer's own warranty lookup for the definitive answer.
What refrigerant does my unit use, based on its age?
It depends on the brand family, and this tool reads the decoded year against that family's own timeline rather than against one industry rule. The boundaries are not shared: across the 23 families this tool documents there are 9 distinct timelines, with era boundaries falling in 1996, 2006, 2008, 2010, 2013, 2024 and 2025, and only 3 of them change over in 2006. What does hold is the newest era: for the 22 families whose record runs to the present it begins in 2024 or 2025 and is an A2L refrigerant, R-454B or R-32 depending on the family. The exception is Janitrol, whose record stops at 1992. Decode the serial above and the tool prints the era for that unit's family and year, with the caveats that family's record carries. The refrigerant printed on the nameplate always wins over any year-based rule.
When should I replace an AC instead of repairing it?
Age is the biggest input, which is why decoding the serial matters. This tool draws the same two lines its result panel draws: from 12 years old a unit is in the repair-or-replace window, and from 18 years replacement is the call on any major repair. Refrigerant matters too: an R-22 unit is almost always a replacement candidate because R-22 is reclaim-only, and R-410A repair costs are rising as the AIM Act phasedown tightens supply. Which of the two a unit holds depends on its family as well as its year, so read the era the decoder prints above rather than a single cutoff.
How does the 2025 R-454B and R-32 transition affect my existing unit?
Nothing forces you to replace an existing R-410A system: it can legally run and be serviced for its whole life. What changes is economics. Virgin R-410A production is being phased down under the AIM Act, so recharge costs trend up, and new equipment manufactured from January 1, 2025 uses lower-GWP A2L refrigerants (R-454B or R-32, depending on brand). A2L refrigerants are mildly flammable, which brings new handling rules, room-size charge limits, and leak-detection requirements, but also a GWP 68 to 78 percent lower than R-410A depending on which one.
Why does the decoder show two possible dates for my serial?
Some formats are genuinely ambiguous and an honest decoder says so. York serials from 1971 to 2004 use year letters that repeat every 21 years, so the letter F means 1976 or 1997. Mitsubishi and LG encode only the last digit of the year, so the decade must come from the refrigerant or the model generation. And the ICP brands (Heil, Tempstar) use a layout that looks identical to Carrier's with the digit pairs swapped, so a serial like 1206A can read as week 12 of 2006 or week 6 of 2012 depending on the brand. When more than one reading passes the validity checks, this tool shows all of them, ranked.
Do all brands encode the date in the serial number?
No. Fujitsu, Senville, and Pioneer serials are sequential and carry no date; for those, look for the separate stamped date code or MFG DATE field on the unit, or contact the manufacturer with the serial. Many Daikin mini splits also carry the date in a separate MFG DATE box instead of the serial. And some formats are documented so inconsistently (Midea and MrCool 22-digit serials, legacy Goodman serials ending in P or D) that this tool declines to guess rather than risk a wrong answer.
What does the week number in a serial mean?
Brands like Carrier, Trane, Rheem, and the ICP family encode the week of the year (01 through 53) instead of the month. Week 01 is early January, week 26 lands around late June, and week 52 is late December. The decoder converts the week to an approximate month for readability, and any week value above 53 is impossible, which is one of the checks this tool uses to reject wrong readings automatically.
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