Furnace Fault Codes

Furnace flashing 5 times: what 5 flashes means

The number of flashes on a furnace control board is not a standard. Every manufacturer assigns its own meanings, and 5 flashes means something different across the 7 control families below.

On an Armstrong it is watchguard — burner failed to light, retries or recycles exceeded, on a Goodman it is flame detected when no flame should be present, and on a Heil it is flame sensed out of sequence — flame signal still present.

Those aren't three flavors of one fault; five flashes means three genuinely different problems depending on who built the board. Nail down the brand before acting on any of them.

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.

5 flashes, by manufacturer

Furnace brandWhat 5 means there
Armstrong
5 flashes		Watchguard — burner failed to light, retries or recycles exceeded
Goodman
5 flashes — Goodman GMS, GMP, GMH, GMV8, GMV9 and Amana AMH, AMV9 series		Flame detected when no flame should be present
Goodman
5 red flashes — GMEC96 / AMEC96		Open rollout switch, or open fuse detected
Heil
5 flashes		Flame sensed out of sequence — flame signal still present
Rheem
5 blinks		Twinning circuit failure
Trane
5 flashes		Flame sensed when no flame should be present
York
5 red flashes		Open rollout switch

Before counting again

Watch for the pause: a blink with no break at all, unlike a counted run of five, is just the board's heartbeat — power is on and nothing's wrong. Every brand's normal-operation patterns are catalogued separately from faults.

Finding out which brand you have

Because many furnaces are sold under a brand name that isn't the control board maker's own, the rating plate inside the cabinet — not the thermostat — is the only reliable place to confirm which one you have. See reading a furnace fault code for help locating it, and for what a numeric display means.

Other flash counts

What the fix costs

If a failed part is what's behind the fault, expect a bill: see what a control board replacement typically costs, or the broader furnace repair cost guide for service-call pricing generally.

What 5 flashes usually points to

5 flashes is mostly a false flame-sensing fault: Goodman, Trane and Heil all report the board seeing a flame signal when the gas valve should be closed, which points at the flame sensor or its wiring rather than the burner itself. Armstrong instead uses 5 flashes for an ignition lockout after repeated failed attempts, and York uses it for an open rollout switch. A false flame reading is safety-relevant on the boards that report it here — treat it per the warning above rather than as a switch or filter to check yourself. That is a different category from 4 flashes' overheat theme and the rollout-and-wiring mix at 6 flashes.

Sources

Behind each five-flash entry here is a manufacturer document, linked from the matching 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.