Furnace Fault Codes

Furnace flashing 6 times: what 6 flashes means

The number of flashes on a furnace control board is not a standard. Every manufacturer assigns its own meanings, and 6 flashes means something different across the 5 control families below.

On an Armstrong it is not used — if you are counting six flashes, count again, on a Goodman it is rollout switch has tripped, and on a Trane it is 115 volt AC power reversed, or poor grounding.

Three brands, three unrelated faults — six flashes doesn't converge on one meaning, and the count by itself is useless. Work out the manufacturer before you act on any of it.

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.

6 flashes, by manufacturer

Furnace brandWhat 6 means there
Armstrong
6 flashes		Not used — if you are counting six flashes, count again
Goodman
6 flashes — Goodman GMS, GMH, GMV8, GMV9 and Amana AMH, AMV9 series		Rollout switch has tripped
Goodman
6 flashes — Goodman GMSS9 and Amana AMSS9 series		Rollout limit open, or control module fuse blown
Goodman
6 red flashes — GMEC96 / AMEC96		Pressure switch cycle lockout
Trane
6 flashes		115 volt AC power reversed, or poor grounding
York
6 red flashes		Pressure switch cycle lockout

Before counting again

Not every blink is a code to count. One that runs continuously, with no gap separating it into groups of six or anything else, is a heartbeat — proof the board is powered and healthy. The complete by-brand list of non-fault patterns covers the rest.

Finding out which brand you have

Skip the thermostat and open the cabinet: the rating plate there names the actual brand, which is often not the same company that built the control board. Reading a furnace fault code covers finding that plate and interpreting a numeric display if yours doesn't flash at all.

Other flash counts

What the fix costs

Should the diagnosis land on a bad part, two cost references apply: typical control board replacement pricing, or the general furnace repair cost guide for what a service call runs.

What 6 flashes usually points to

6 flashes is a smaller, more mixed group: Goodman reports a tripped rollout switch — flame escaping the burner compartment instead of going up the heat exchanger — while Trane reports reversed AC power or a poor ground, and York a pressure-switch lockout. Armstrong does not use 6 flashes at all. A tripped rollout switch is a gas-safety fault covered by the warning above; reversed power or bad grounding is an electrician's job, not a reset. Unlike 5 flashes' flame-sensing theme or 7 flashes' limit-and-lockout theme below, there is no single failure mode shared across brands at 6 flashes — the manufacturer matters more than usual here.

Sources

These six-flash definitions are drawn from the manufacturer manuals cited on the individual code pages:

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.