Furnace Fault Codes

Furnace flashing 8 times: what 8 flashes means

The number of flashes on a furnace control board is not a standard. Every manufacturer assigns its own meanings, and 8 flashes means something different across the 6 control families below.

On an Armstrong it is rollout switch open, on a Goodman it is igniter circuit fault, most often caused by poor grounding, and on a Heil it is high pressure switch closed when it should be open.

Three brands, three separate faults with nothing in common — that all three land on eight flashes is coincidence, not shared cause. Identify the manufacturer first, then act.

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.

8 flashes, by manufacturer

Furnace brandWhat 8 means there
Armstrong
8 flashes		Rollout switch open
Goodman
8 flashes — Goodman GMH, GDH, GCH and Amana AMH series		Igniter circuit fault, most often caused by poor grounding
Goodman
8 red flashes — GMEC96 / AMEC96		External lockout — recycles exhausted
Heil
8 flashes		High pressure switch closed when it should be open
Trane
8 flashes		Low flame sense signal
York
8 red flashes		Lockout on recycles, flame dropouts

Before counting again

If there's no gap breaking the blink into a group — eight or otherwise — it isn't a code at all; it's the board's heartbeat, confirming power and a clean bill of health. Normal patterns, listed by brand, cover everything that isn't a fault.

Finding out which brand you have

Since a lot of furnaces carry a badge name that isn't the control board maker's, the only place to actually confirm the brand is the rating plate inside the cabinet, not the thermostat. Reading a furnace fault code covers locating that plate and what a numeric display means instead of flashes.

Other flash counts

What the fix costs

For a confirmed failed part, pricing comes next: see the typical cost of a control board replacement, and the general furnace repair cost guide for what a service call adds on top.

What 8 flashes usually points to

8 flashes splits between two problems: Armstrong and Heil report it for the rollout or high-pressure switch, while Goodman reports an igniter circuit fault most often caused by poor grounding — the same grounding theme that shows up at 6 and 9 flashes on other brands. Trane reports a low flame-sense signal instead, and York a lockout following repeated flame dropouts. A rollout fault is gas-safety relevant and belongs with the warning above rather than a reset. That makes 8 flashes more of a grounding-and-hardware group than 7 flashes' limit-switch theme or the pressure-and-wiring group at 9 flashes.

Sources

The eight-flash readings above each cite a manufacturer document, found via the linked 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.