How old is my Comfortmaker furnace or air conditioner?

By Dana Whitlock. Updated October 2026. Widely documented.

A lot of Comfortmakers from the early 1990s are still heating houses, and their plates read the same as new ones. Skip the opening letter. Digits two and three are the build year and digits four and five are the week, so a serial beginning R92 is a 1992 unit and L97 is 1997.

The layout has stayed put for decades across the whole International Comfort Products family. Only some Inter-City era labels from before it need a different approach.

Where to find the label on a Comfortmaker furnace

Comfortmaker furnaces keep the rating plate inside, on the back of the blower door or on the cabinet wall behind it. Turn the furnace off at the service switch, lift the door straight out, and read with a flashlight. Outdoor Comfortmaker units show the plate on the exterior cabinet, low on one corner more often than not, so look rather than open anything. If sun has faded the plate, a photo with the flash on can bring the stamped characters back.

How to read the code

Position 1: a letter for the factory. Positions 2 and 3: the year, where 80 to 99 are 1900s years and 00 forward are 2000s years. Positions 4 and 5: the week, 01 through 53. Everything after that is a sequence number. A plate reading R921500600 comes out as 1992, week 15, which lands in April.

Real serials in this code

When the format changed

A Comfortmaker example posted by a home inspector, R883512345, decodes to week 35 of 1988, and utility contractor references read the brand the same way. The 2005 CPSC recall of ICP packaged units named Comfortmaker and quoted the same pattern as the typical format. Before this layout, some Inter-City era labels used one year digit or a numeric string with a mid-string letter, and the tool will not guess at those. Fall back on the plate's printed date, the installer's invoice or a building permit if you have one of those older labels.

Who makes Comfortmaker

Comfortmaker comes from International Comfort Products of Lewisburg, Tennessee, which also builds Heil, Tempstar, Arcoaire and KeepRite. ICP pitches Comfortmaker as its quiet-running line. Carrier bought ICP in 1999 and left the brand names and distribution alone. All five brands share factories and serial formats, so parts and service manuals overlap a lot even when the badges differ.

How sure is this?

Widely documented. Comfortmaker 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 Comfortmaker's warranty page before you spend money on the answer.

Quick notes

• A Comfortmaker built before 2000 shows a 9 in the second position; anything starting with a letter and then 0, 1 or 2 is from 2000 or later.
• Comfortmaker registration runs through ICP and has a 90-day window for the full 10-year parts term.
• When a contractor quotes a replacement, ask for the serial of the old unit on the paperwork; it documents the age you paid to replace.
• If the tool rejects the serial, recheck letter O versus digit 0 on the plate.