6 components coveredField manual · Fundamentals
Reading model and serial numbers to estimate build date and platform
Covers: General methods for US major appliances; one widely documented example (GE serial month letter). Brand-by-brand decoding lives in the OnCall Tech brand reference; only decodes confirmed by 2+ sources are published as verified
The build date tells you which platform, parts revision and service bulletins apply, whether the unit may still be under warranty and whether a repair makes economic sense. Model numbers identify the platform; serial numbers usually carry the date in a code that differs by brand and era. Never guess a date from a single letter when the code repeats.
Safety first
- Some labels are behind kick plates or inside compartments: power off before removing panels near wiring
How it works
The model number identifies the product family and configuration; the trailing characters often mark a revision or engineering change, and parts lists are tied to that full string. Always copy it exactly, including the suffix.
Serial numbers are unique per unit and most brands embed the build month and year, often as letters or digits in fixed positions. The code differs by brand and has changed over the years within the same brand.
Many codes cycle. GE's serial uses a first letter for the month and a second letter for the year on a repeating 12-letter cycle, so the same letter maps to years 12 apart. Narrow the decade with other clues: the model generation, the date on the paper manual or tech sheet, the refrigerant type, the style of the control or the date stamped on parts.
Some labels print the date in plain text (month/year or full date). When a plain date exists, use it over any decode.
When no decode is confirmed, ask the manufacturer's support line or check the warranty registration; do not tell a customer a date you inferred from an unconfirmed table.
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Always confirm values against the tech sheet for the exact model.
- CPSC recalls search
- SaferProducts.gov recall and incident search
- Whirlpool Corporation recall information
- GE Appliances recalls
- Frigidaire recall information
- Water heater and boiler recall lookup (A. O. Smith / Lochinvar)
- EPA Section 608 technician certification types
- OSHA control of hazardous energy (lockout/tagout)
- CPSC carbon monoxide information center
OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.
