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Home > Error Codes > Armstrong Air
Every documented Armstrong Air furnace error code with causes, fixes, and the parts you may need. Also covers: Armstrong Air, Aire-Flo, Ducane, Concord, Allied Air.
Steady ON
Control Board Failure
Internal board fault.
DIY check: Power cycle. Replace board if solid ON persists.
Common part needed: Shop Control Board →
Steady OFF
No Power
No power to board.
DIY check: Check breaker, switch, door switch, fuse, transformer.
Common part needed: Shop Transformer →
1 Flash
Open High Limit
High-temperature limit switch tripped from overheating.
DIY check: Check air filter, registers, blower motor, ductwork restrictions.
Common part needed: Shop Fan Motor →
2 Flashes
Pressure Switch Stuck Closed
Pressure switch closed before inducer operation.
DIY check: Check for stuck switch, water in hose. Replace if repeated.
Common part needed: Shop Pressure Switch →
3 Flashes
Pressure Switch Open
Pressure switch did not close after inducer started.
DIY check: Check condensate drain, vent, pressure hose, inducer motor.
Common part needed: Shop Pressure Switch →
4 Flashes
Open Fuse on Board
The board fuse has blown. No 24V to thermostat.
DIY check: Find and fix the short circuit in thermostat wiring, then replace the fuse.
Common part needed: Shop Transformer →
5 Flashes
Flame Without Gas Valve
Flame detected when gas valve is off. Safety issue.
DIY check: Turn off furnace and gas. Call a technician.
Common part needed: Shop Gas Valve →
6 Flashes
115V Reversed / No Ground
Power polarity reversed or missing ground.
DIY check: Check and correct wiring polarity and ground connection.
7 Flashes
Flame Lost / Flame Failure
Flame was established then lost during the heating cycle.
DIY check: Clean flame sensor. Check gas pressure. Check for drafts.
Common part needed: Shop Flame Sensor →
8 Flashes
Ignition Lockout
Failed to ignite after maximum retries.
DIY check: Power cycle to reset. Check igniter, gas supply, flame sensor.
Common part needed: Shop Igniter →
9 Flashes
Check Gas Supply / Valve
Gas valve not opening or insufficient gas supply.
DIY check: Verify gas is on at meter and at manual shutoff. Check gas valve operation. May need technician for gas pressure test.
Common part needed: Shop Gas Valve →
10 Flashes
Blower Motor Overcurrent
The blower motor is drawing excessive current.
DIY check: Check for seized blower wheel, failed capacitor, or motor bearing failure.
Common part needed: Shop Fan Motor →
Rapid Flash
Line Voltage Brownout
Incoming power dropped below acceptable levels.
DIY check: Check electrical connections. May be utility issue or shared circuit overload.
If the same code keeps coming back after you have addressed the obvious cause (dirty filter, flame sensor, etc.), or if you smell gas, see burn marks, or the furnace will not come out of lockout after a power cycle, call a licensed HVAC technician. Electrical and gas work carries real safety risk.