Furnace Troubleshooting & Error Codes
The furnace pages are organised around the code a furnace's control board shows. Carrier furnaces flash a two-digit status code on an LED, short flashes then long. Goodman furnaces flash a count on one LED or on red, amber and green LEDs, or show a short code on a display, depending on the series. Rheem furnaces show a two-digit code on a display or, on older series, blink a status LED. The Bryant/Payne hub covers three model families with their own tables.
Every meaning is read from the manufacturer's installation instructions, troubleshooting guide or service bulletin and cited by document number and page. The same flash count can mean different things on different control boards, so start from the furnace model on the rating plate, then open the brand hub, then the code.
The pages go as far as the manuals let an owner go — reading the code, the filter, a look at the burner flame — and stop where the manuals require a qualified servicer. Gas and carbon monoxide guidance comes from the CPSC and from the manufacturers' own warnings.
How these pages are sourced
Every code meaning on this site comes from the manufacturer's published installation instructions, service literature or owner's manual, cited by document number and page. Where a manufacturer's own documents disagree between furnace generations, both readings are given rather than averaged into one answer. No forum, video or repair-shop blog is used as a source for a code meaning.
Safety guidance that is not manufacturer-specific comes from the U.S. Consumer Product Safety Commission. We do not publish a repair procedure that the manufacturer reserves for trained service personnel, which on a gas furnace is nearly all of them.