SerialAtlas
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HVAC date-code guide

Lennox serial number lookup

Lennox has used a stable position-based serial convention for decades: the third and fourth characters indicate year and the fifth letter indicates month.

Parent
Lennox International / Allied Air
Common code
For the common current style, characters 3–4 are the year and character 5 is a month letter.
Reviewed
August 8, 2026

Instant equipment lookup

Decode the manufacturing date

Runs on this device
Equipment type

Using For the common current style, characters 3–4 are the year and character 5 is a month letter.

Type exactly what is printed. Spaces and dashes are ignored.

Optional: add model number for capacity cluesAdd model

Model decoding is labeled as a clue unless the exact format is documented.

No signupNo uploadNo serial-number tracking

EQUIPMENT DATA
MODEL24ABC636A003
SERIAL5019X30312
WeekYear

See exactly how the code was read

SerialAtlas highlights the date characters, names the matching rule, and shows alternative interpretations when the code is ambiguous.

  • Current age calculated automatically
  • Confidence and rule source shown
  • Optional model-capacity clue

Evidence-led route update

Lennox date-code evidence

If you need to estimate a Lennox unit’s manufacture age, start with the serial number on the rating plate.

Read characters 3–5 as one family block

For the common current style, characters 3–4 are the year and character 5 is a month letter. The common Lennox-family read uses characters 3–4 for the year and character 5 for a month letter. Armstrong Air and Ducane share this family, but the brand and equipment line still matter. Use characters 3–4 for the year and character 5 for the month letter in the documented Lennox-family block. The label location and equipment type help distinguish a Lennox residential unit from an older or imported product that needs another reference.

Worked example: 5196G12345

5196G12345 — The verified decoder reads this fixture as July 1996. The date is a manufacture estimate, not an installation date.

When a Lennox letter is not enough

A month letter can be unreadable or the unit can belong to a legacy or imported line. Preserve the complete model and serial, then compare the rating plate with the official support route before using the date for a warranty or replacement decision.

Model number vs. serial number

Use the model number to identify the Lennox product family and the serial number to estimate manufacture age; provide both for parts or warranty support. Record the complete Lennox model and serial together; the model identifies the product family while the serial supplies the date-code evidence.

Limits and official support

Legacy and imported Lennox-family equipment can use another format. If the result affects warranty, registration, parts, safety, or replacement decisions, use the complete model and serial with the manufacturer or a qualified professional. SerialAtlas is an independent reference, not an official warranty lookup or warranty coverage decision.

Open Lennox support route

How to read a Lennox serial number

For the common current style, characters 3–4 are the year and character 5 is a month letter. SerialAtlas removes spacing and punctuation, then applies only the documented rule families mapped to Lennox. The lookup remains in the browser.

Try this documented-style example5196G12345Load example

Equipment covered

  • air conditioners
  • heat pumps
  • furnaces
  • air handlers
  • packaged systems

Commercial, imported, very old, specialty, and private-label equipment can use a different code. Confirm the full rating plate before accepting a result.

Where to find the rating plate

  • Outdoor condenser or heat-pump cabinet, usually near the service valves
  • Inside the furnace or air-handler access panel
  • On the packaged-unit rating plate
  • Near the electrical disconnect or wiring diagram

Why more than one date can appear

Two-digit years and repeating letter cycles can point to more than one era. SerialAtlas ranks the plausible dates but keeps materially different alternatives visible. Label design, refrigerant, installation records, and product literature can resolve the era.

Source and verification

Inspector Handbook open reference data (CC BY 4.0). Independently implemented and reviewed August 8, 2026.

Open reference source

What this result does not prove

A manufacture date is not an installation date, warranty decision, recall match, condition assessment, or replacement recommendation. Confirm high-stakes decisions with the manufacturer or a qualified professional.