How old is my Ruud furnace or AC?

By Dana Whitlock. Updated October 2026. Widely documented.

The quickest answer is printed on the plate. Ruud rating plates on furnaces, air conditioners and heat pumps usually show 'MFD.' and a date in the upper right, written as MM/YY or MM/YYYY. MFD. 07/04 means the unit was built in July 2004.

If that line is missing or worn off, use the serial. Scan it from right to left until you hit a letter. The two digits after that letter give the week, and the next two give the year. An inspector's photo of a Ruud plate shows M3004 in the serial (week 30 of 2004) beside a printed MFD. 07/04, so the two methods agree. We rate this Widely documented.

Where to find the label on a Ruud furnace

Indoor Ruud equipment (furnaces and air handlers) has the plate on the inside of the cabinet, visible once the front door is lifted off. Shut the thermostat off and switch off the service switch beside the unit before opening it. Hold a flashlight at an angle to make faded print readable, and take a photo instead of leaning in. On an outdoor Ruud condenser or heat pump, check the side panels of the cabinet. If the only way to see a label is to unscrew a panel, leave it for a licensed HVAC technician.

How to read the code

Ruud serials do not have a fixed length, so position counting fails. Going right to left is faster: the first letter you meet is the last letter in the serial, and the date is the four digits after it. Example, using a serial from a Rheem-built condenser that reads the same way: 6263F270311112 has its final letter at F, then 27 and 03. That is week 27 of 2003, early July. If the four digits after the final letter give a week of 00 or more than 53, look again, because you may be reading the model number. Two-digit years from 40 to 99 belong to the 1900s and 00 to 39 to the 2000s.

Real serials in this code

When the format changed

Ruud's heating and cooling code has stayed stable for decades. When Rheem recalled oil furnaces in 2009, the notice defined the date code as the four digits after an M in the middle of the serial, with week and year, for units sold January 2006 through December 2008. Ruud data tags from 2006 and 2007 photographed by InspectAPedia show the printed MFD dates too. Two exceptions. Ruud water heaters follow other rules entirely, and some units built before the 1980s placed week and year in the last four digits instead. When the decoded date and the printed MFD date disagree, the printed date is right. Ruud's online warranty lookup is another cross-check.

Who makes Ruud

Ruud is one of the Rheem family of brands, and Rheem Manufacturing builds both. Rheem and Ruud furnaces, air handlers and outdoor units share the same last-letter week-and-year date code, so a Rheem guide gives the same result on a Ruud unit. Ruud is sold through independent heating and cooling contractors.

How sure is this?

Widely documented. Ruud doesn't publish this code; it comes from recall notices, service literature and inspector references. We tested the rheem ruud hvac rules against 5 serials, 2 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 Ruud's serial lookup before you spend money on the answer.

Quick notes

• Check the upper right corner of the plate for an MFD date before anything else.
• Reading the serial from right to left finds the date code fastest.
• Two Ruud condensers in one house with serials close together were probably installed on the same job.
• A Ruud water heater in the same basement needs a different chart; do not mix the two.