Furnace Fault Codes

Furnace flashing 9 times: what 9 flashes means

The number of flashes on a furnace control board is not a standard. Every manufacturer assigns its own meanings, and 9 flashes means something different across the 6 control families below.

On an Armstrong it is pressure switch failed to close, or opened during a heat demand, on a Goodman it is high stage pressure switch stuck open, and on a Heil it is high pressure switch open when it should be closed.

Nine flashes isn't a single fault with brand-specific wording; it's three unrelated problems that happen to share a count. Start with the brand before acting 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.

9 flashes, by manufacturer

Furnace brandWhat 9 means there
Armstrong
9 flashes		Pressure switch failed to close, or opened during a heat demand
Goodman
9 flashes — GMV8 / GMV9 / AMV9		High stage pressure switch stuck open
Goodman
9 red flashes — GMEC96 / AMEC96		Grounding problem or reversed polarity
Heil
9 flashes		High pressure switch open when it should be closed
Trane
9 flashes		Ignitor circuit problem, or low voltage between neutral and 24 volt common
York
9 red flashes		Grounding, reversed polarity, or reversed transformer leads

Before counting again

An unbroken, even blink — no pause splitting it into nine or any other count — signals a heartbeat rather than a fault: the board is powered and has nothing to report. Each brand's normal, non-fault patterns are listed on their own page.

Finding out which brand you have

The rating plate inside the cabinet — not the thermostat — is where the real brand shows up, and it's often a different company than whoever built the control board. If you can't find it, or your furnace shows a number rather than blinking, reading a furnace fault code covers both.

Other flash counts

What the fix costs

If the diagnosis lands on a genuinely failed component, see the typical cost to replace a control board, or the general furnace repair cost guide for service-call pricing.

What 9 flashes usually points to

9 flashes is a high-stage pressure-switch fault on Goodman and Heil, a pressure switch that failed to close on Armstrong, and a grounding or reversed-polarity problem on Trane and York — the same wiring theme that appears at 6 and 8 flashes on other brands. Because a bad ground or a reversed transformer lead can cause other faults to show up intermittently, it is worth ruling out before chasing the pressure switch. That is a narrower, more electrical-leaning group than 8 flashes, and by 10 flashes below, only three of these manufacturers still assign the count a meaning at all.

Sources

Each nine-flash interpretation on this page is grounded in the manufacturer literature its code page links:

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.