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.
Decode schemes compiled from manufacturer literature and inspector references (Building Center, InspectAPedia, How To Look At A House, ICP parts documentation), cross-checked across two sources wherever possible. Single-sourced rules are labeled low confidence in the results instead of being presented as fact, and 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 every brand in it. 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 + 5 digits | Digits 3-4 (digits 1-2 are the week) | R-454B (Puron Advance) |
| Heil, Tempstar, Comfortmaker, Arcoaire, KeepRite, Airquest | Letter + 9 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 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 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). When both digit pairs are 53 or less, only the brand on the nameplate can settle it.
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, and at least one widely copied chart publishes them backwards. 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.
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 usually labeled S/N or SERIAL and is longer than the model number.
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. Warranties are almost never transferable at full term, so a home's second owner usually holds the shorter base coverage. 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?
As a rule of thumb for US residential equipment: manufactured before about 2006, R-22; 2006 to 2009, either R-22 or R-410A depending on the model line; 2010 through 2024, R-410A; and 2025 onward, an A2L refrigerant, which is R-454B for Carrier, Trane, Lennox ducted, Rheem, York, and most legacy brands, and R-32 for Goodman, Amana, Daikin, LG, Samsung, Gree, and Fujitsu. Carrier is a special case: it launched R-410A (Puron) back in 1996. The refrigerant printed on the nameplate always wins over any year-based rule.
When should I replace an AC instead of repairing it?
The common field rule is the 5,000 rule: multiply the unit's age by the repair quote, and if the product exceeds 5,000, lean toward replacement. Age is the biggest input, which is why decoding the serial matters. Past 15 years, most units are on borrowed time; past 20, major repairs rarely pay off. Refrigerant matters too: R-22 units (pre-2010) are almost always replacement candidates because R-22 is reclaim-only, and R-410A repair costs are rising as the AIM Act phasedown tightens supply.
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 roughly 75 percent lower GWP.
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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