Furnace blink decoder
Watch the light through the furnace sight glass for two full cycles, then describe it below. Every match links to a code page verified against the manufacturer's service manual.
Smell gas, hear a CO alarm, or see flames outside the burner? Don't decode anything — follow the six emergency signs →
1 · Brand
Choose the control family and LED color when known. Count complete repeat cycles, keeping short and long flashes separate, and compare the pattern with your furnace's manual.
2 · What do you see?
3 · Match
Pick a brand and pattern above.
Matched a code marked PRO — or can't get a clean match after two full cycles? A licensed tech can pull the board's fault history in one visit.
Every verified pattern, by brand
Prefer to scan? Every pattern the decoder knows, with the page it links to. Codes are bound to the model series listed on each page — the same flash count can mean different things on different generations.