Furnace flashing 11 times: what 11 flashes means

The number of flashes on a furnace control board is not a standard. Every manufacturer assigns its own meanings, and 11 flashes means something different on each of the 3 control families below.

These are not variations on one fault. They are entirely different problems, and the count alone does not distinguish them. Identify the manufacturer before acting on any of them.

Some of the faults listed here are gas-safety faults. Those ones involve the gas valve, the burner compartment, or the heat exchanger — the parts whose failure can put combustion products, including carbon monoxide, into the air the house breathes, and each carries this warning on its own page. Do not keep resetting a furnace that reports one of them in order to hold the heat on. Have it looked at by a licensed technician, and make sure there is a working carbon monoxide alarm on every level of the home, including the level the furnace is on. The conditions that mean stop now.

11 flashes, by manufacturer

Furnace brand	What 11 means there
Armstrong 11 flashes	Pressure switch stuck closed before the inducer started
Goodman 11 red flashes	Limit switch open due to blower failure
York 11 red flashes	Limit switch open more than five minutes — blower failure

Before counting again

An even, unbroken blink with no pause is a heartbeat, not a code — it means the board is powered and has found nothing wrong. Every pattern that is not a fault lists them by brand.

Finding out which brand you have

The brand is printed on a rating plate inside the furnace cabinet, usually on the inner wall behind the removable front panel, and often repeated on a sticker on the outside of that panel. The name on the thermostat is not reliable — thermostats are replaced far more often than furnaces, and a great many furnaces are sold under a different name from the company that built the control board. The brand hubs below list the alternative names each manufacturer sells under.

Goodman — also Amana
Carrier — also Bryant, Payne
Trane — also American Standard
Lennox
York — also Luxaire, Coleman
Rheem — also Ruud, Weather King
Heil — also Tempstar, Comfortmaker, Arcoaire, KeepRite
Armstrong — also AirEase, Concord, Ducane

If the furnace shows a number rather than flashes

Several manufacturers stopped using flash counts and display a two-digit status code or a letter-and-digit code on a seven-segment display instead. If what you are reading is a number on a small screen rather than a light going on and off, count nothing — read the code directly and look it up on the manufacturer's page.

Other flash counts

Sources

Every meaning on this page comes from the manufacturer document behind its code page:

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.