Armstrong Air, AirEase, Concord and Ducane furnace codes

Allied Air controls store the last ten faults and keep them through a power cut — the most generous fault memory of any furnace control documented here.

Also covers: AirEase, Concord, Ducane — same manufacturer, same controls, same codes.

Armstrong Air, AirEase, Concord and Ducane are all Allied Air Enterprises, and they share integrated controls and code tables. The -02 control uses a red LED: a slow heartbeat of one second on and one second off means healthy, and counted flashes are faults. Its most useful feature is the stored error history — the last ten codes, retained even when power is shut off to the unit.

Worth knowing before you count

Because the history survives a power cut, switching the furnace off and on does not destroy the evidence the way it does on most other manufacturers. But holding the recall button for more than five seconds does. Press and release to read; do not hold.

How these furnaces signal codes

The -02 control uses one red LED for everything. Healthy is a heartbeat — one second on, one second off — and faults are counted flashes from one to thirteen, with six unused. The low counts are unusual among the brands on this site: one flash, two flashes and thirteen flashes are reversed polarity, improper earth ground and low line voltage — the control complaining about the house's electrical supply rather than about the furnace. To replay the stored history, press and release the button on the control: the most recent code shows first, the LED goes dark for three seconds, then the next plays, through up to ten codes. Write them down as they appear — ten codes at three-second intervals is more than most people can hold in their head — and give a technician the sequence, not just the newest code, because the order shows how the fault developed.

The codes people look up most

Three flashes — the burner failed to light or lost flame during a heat demand — is the most common path to a cold house, and its escalation, five flashes, is the Watchguard lockout after the retries run out. Four flashes, a low flame signal, is the code a dirty flame sensor produces and the cheapest fix on the list. Nine flashes is the pressure switch failing to close or opening mid-demand, a draft question before a parts question; ten flashes is its Watchguard form after five openings in one demand. Seven flashes is an open limit — airflow first — and eight flashes, an open rollout switch, means flame left the burner compartment and is a call-a-professional code, not a reset code.

Which models these pages cover

These pages are documented from Table 7 of Allied Air Enterprises installation instructions 507330-03, covering the A80UH1E and 80G1UHE gas furnaces with the -02 integrated control. Allied Air sells the same equipment as Armstrong Air, AirEase, Concord and Ducane, so the codes carry across all four nameplates. For furnaces outside these model families, the code legend printed inside the access panel is the authoritative reference for that specific unit.

What the common fixes cost

Four flashes usually ends at flame sensor cleaning: $80–200, the classic ten-minute fix — worth ruling out before anything else on three- and five-flash ignition failures too, since a sensor that cannot prove flame looks identical to a burner that never lit. A genuinely failed igniter runs $150–350 installed, part only $20–60. Pressure switch codes (nine, ten and eleven flashes) are $150–400 with the flue and venting checked first. An open limit at seven flashes is $150–350 plus the airflow diagnosis, and a rollout at eight flashes is priced the same but is really a why-did-flame-escape investigation rather than a part swap. An LED that stays dark with power confirmed points at the control: a $5–150 fuse first, then the $400–900 board.

Armstrong Air, AirEase, Concord and Ducane

1 flash — Reverse line voltage polarity
2 flashes — Improper earth ground
3 flashes — Burner failed to light, or lost flame during a heat demand
4 flashes — Low flame signal — check the flame sensor
5 flashes — Watchguard — burner failed to light, retries or recycles exceeded
6 flashes — Not used — if you are counting six flashes, count again
7 flashes — Primary or secondary limit open, or Watchguard after three minutes open
8 flashes — Rollout switch open
9 flashes — Pressure switch failed to close, or opened during a heat demand
10 flashes — Watchguard — pressure switch opened five times during one heat demand
11 flashes — Pressure switch stuck closed before the inducer started
12 flashes — Flame sensed without the gas valve energised
13 flashes — Low line voltage
Error code recall — The last ten faults, retained even through a power cut
Heartbeat — Control powered, no errors detected
LED off — No power to the control, or a control hardware fault

Other manufacturers

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.