What is your furnace trying to tell you?
Look up the flash code or error code on your furnace, heat pump, or mini-split. 672 codes across 16 brands, every one cited to the manufacturer's own manual with a link to the exact PDF and the date we checked it.
Pick your brand
Amana
40 codes · Furnace, Air Conditioner
American Standard
28 codes · Furnace
Bryant
39 codes · Furnace
Carrier
28 codes · Furnace
Coleman
47 codes · Furnace
Daikin
58 codes · Mini-Split
Fujitsu
47 codes · Mini-Split
Goodman
40 codes · Furnace, Air Conditioner
Lennox
44 codes · Furnace
LG
48 codes · Mini-Split
Mitsubishi Electric
53 codes · Mini-Split
Payne
34 codes · Furnace
Rheem
40 codes · Furnace
Ruud
40 codes · Furnace
Trane
38 codes · Furnace
York
48 codes · Furnace
1. Count the flashes
Most furnaces blink an LED behind a small window in the lower door. Count the pattern — short and long flashes matter. Mini-splits show a code on the unit or remote.
2. Look it up by brand
The same count means different things on different brands. Every page here quotes the brand's own manual, so you are reading what the manufacturer says, not a guess.
3. Check the safe stuff first
Filters, vents, switches, and drain clogs fix a surprising share of codes. Anything past that is a job for a licensed technician — each page says which is which.
How old is your system?
The serial number on the rating plate has the build date in it. Age is what decides whether a fault code means a repair or a replacement, so it is worth knowing before you get a quote.