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.

Armstrong Air, AirEase, Concord and Ducane

Heartbeat — Control powered, no errors detected
Error code recall — The last ten faults, retained even through a power cut
LED off — No power to the control, or a control hardware fault
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
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

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.