Armstrong Air Furnace 9 flashes: What It Means & How to Fix It
Compiled & reviewed by the HVAC Flash Codes editorial team · Updated 2026-06-25 · confidence: high
⛔ Stop — call a licensed pro
What does Armstrong Air furnace 9 flashes mean?
Pressure switch failed to close, or opened during a heat demand — the combustion-air/vent pressure switch did not prove adequate draft. Most often caused by A blocked or restricted intake/exhaust vent (debris, ice, snow, nests).
What your furnace LED does. The diagnostic light blinks 9 flashes, pause, repeat — that pattern is Armstrong Air furnace 9 flashes.
What Armstrong Air furnace 9 flashes means
Pressure switch failed to close, or opened during a heat demand — the combustion-air/vent pressure switch did not prove adequate draft.
Common causes
A blocked or restricted intake/exhaust vent (debris, ice, snow, nests)
A failed or weak combustion-air inducer
A disconnected/kinked pressure-switch hose or condensate blockage
Homeowner-safe steps to try
From outside, check that the intake and exhaust terminations are clear of snow, ice, leaves, or debris
Replace a dirty filter and confirm vents are open
A single power cycle may be tried; if the code returns, call a pro — do not adjust or bypass the pressure switch
When to call a licensed HVAC technician
If the basic checks below don't clear the code, the fault recurs, or anything involves the gas valve, burners, flame sensor or wiring, stop and book a licensed HVAC technician. Repairs to the combustion or gas system are not DIY.
⚠️ Safety first. Gas furnaces burn fuel and produce combustion gases. If you ever smell gas (a rotten-egg or sulfur odor), hear hissing, or your carbon-monoxide alarm sounds, do not touch light switches, thermostats, or the furnace — leave the home immediately and call your gas utility's emergency line or 911 from outside. Homeowners should limit themselves to simple, safe steps: setting the thermostat, checking and replacing the air filter, confirming the furnace switch and breaker are on, keeping supply registers and return grilles open, and clearing snow, ice, or debris from outdoor vent and intake terminations. Never bypass, jumper, or reset safety switches (limit, flame-rollout, or pressure switches), never open the gas valve or burner compartment, and never attempt combustion, electrical, or control-board repairs yourself. Error codes point toward a problem but are not a substitute for proper diagnosis — when in doubt, turn the system off and call a licensed HVAC technician. Keep working carbon-monoxide detectors on every level of your home.
When to call a pro: If venting looks clear but the code persists, call a licensed HVAC technician to test the inducer, hoses, and pressure switch. Never bypass a pressure switch — it protects against unsafe venting/CO. If you smell gas or a CO alarm sounds, leave and call 911 or the gas utility from outside.
Armstrong Air furnace 9 flashes FAQ
What does Armstrong Air furnace 9 flashes mean?
Pressure switch failed to close, or opened during a heat demand — the combustion-air/vent pressure switch did not prove adequate draft.
What causes Armstrong Air furnace 9 flashes?
Common causes: A blocked or restricted intake/exhaust vent (debris, ice, snow, nests); A failed or weak combustion-air inducer; A disconnected/kinked pressure-switch hose or condensate blockage.
Can I fix Armstrong Air furnace 9 flashes myself?
You can safely try: From outside, check that the intake and exhaust terminations are clear of snow, ice, leaves, or debris; Replace a dirty filter and confirm vents are open; A single power cycle may be tried; if the code returns, call a pro — do not adjust or bypass the pressure switch. If venting looks clear but the code persists, call a licensed HVAC technician to test the inducer, hoses, and pressure switch. Never bypass a pressure switch — it protects against unsafe venting/CO. If you smell gas or a CO alarm sounds, leave and call 911 or the gas utility from outside.
Sources: firstsupply.com. General information for homeowners, not professional advice — confirm against your furnace's manual and a licensed technician.