How old is my Tempstar furnace or air conditioner?

By Dana Whitlock. Updated October 2026. Widely documented.

Tempstar puts the year first, even though Carrier, which owns its parent company, puts the week first. Ignore the opening letter, read the next two digits as the year and the two after those as the week. G0516 means the 16th week of 2005.

The layout has held steady from at least 1988 into the current decade. A home inspector photographed a 2013 Tempstar plate that still followed it, well after Carrier took over the parent company.

Where to find the label on a Tempstar furnace

Tempstar condensers and heat pumps carry a rating plate on the outside of the cabinet, usually on the panel by the service valves. Furnaces keep it inside, on the blower or burner compartment door or the cabinet wall behind it. Shut the furnace off at the switch before opening a door, and never open the outdoor unit's panels at all. Some Tempstar plates also print a manufacture date in month/year form, which saves the arithmetic.

How to read the code

Think of it as L + YY + WW + sequence. The letter is the factory. YY is the year: 80 to 99 means the 1900s, 00 and up means the 2000s. WW is the production week from 01 to 53. The rest is a running count that tells you nothing about age. The tool converts the week into a likely month, but week 01 or week 52 can spill into the neighboring month, so treat the month as close rather than exact.

Real serials in this code

When the format changed

The best cross-check comes from a Tempstar tag shown on Building-Center.org: serial L920671787 with a printed MFG. DATE of 2/92. Year 92, week 06, February. That agreement is why the tool trusts this layout. What it does not read: older Inter-City style labels with only one year digit, all-numeric serials with a letter buried mid-string, or serials beginning with Z. For those, use the printed date if the plate has one, or the permit and invoice from installation.

Who makes Tempstar

Tempstar is an International Comfort Products brand, built in the same Lewisburg, Tennessee operation as Heil, Comfortmaker, Arcoaire and KeepRite. ICP positions Tempstar around efficiency and technology. Carrier agreed to acquire ICP in 1999 for about $490 million plus assumed debt and said at the time the brands and distributor network would stay intact. You buy Tempstar through local dealers. It isn't on retail shelves.

How sure is this?

Widely documented. Tempstar doesn't publish this code; it comes from recall notices, service literature and inspector references. We tested the icp rules against 15 serials, 5 of them with a date known from a recall notice, a printed label date or the maker. None decoded to a wrong year; codes whose year mark repeats show every possible reading. Always confirm with Tempstar's warranty page before you spend money on the answer.

Quick notes

• If the plate prints a MFG. DATE, trust it over any decode, including ours.
• Write the serial with the letter included when you type it into the tool; it checks the pattern.
• Tempstar's parts warranty is 10 years if registered within 90 days, otherwise 5. Ask the seller of a newer home whether it was registered.
• A furnace and a condenser installed together are often built weeks apart; date each one separately.