Armstrong furnace 6 flashes: Not used — if you are counting six flashes, count again
Allied Air lists six flashes as not used on this control. The table runs from one to thirteen and skips six deliberately, so a genuine six-flash count is not a code — it means the count is wrong.
Applies to: Armstrong Air, AirEase, Concord and Ducane gas furnaces using the Allied Air -02 integrated control, as documented in installation instructions 507330-03, Table 7.
What it means
Every other count on this control from one to thirteen carries a meaning, which makes six conspicuous by its absence. Miscounting is easy on this board and there are three usual reasons. The first is the heartbeat: healthy operation is a slow one-second-on, one-second-off pulse, and someone joining it midway can read a run of pulses as a fault count. The second is starting to count mid-pattern, so a seven-flash code becomes six. The third is the pause — the control separates repetitions with a gap, and a count begun in the wrong place straddles two repetitions. The reliable method is to watch through at least three complete cycles and take the count that repeats, rather than the first one you see.
Most common causes
- Counting from part way through a longer pattern, most often the seven-flash limit code.
- Reading the slow heartbeat as a fault count rather than as normal operation.
- Starting the count in the middle of the pause between repetitions.
- A five or seven flash code miscounted by one in poor light, which is the common case.
How to diagnose it
- Watch at least three full repetitions and take the count that appears every time.
- Note whether the pulses are evenly slow and even in length — that is the heartbeat, not a code.
- If the count settles on seven, that is the primary or secondary limit code, which is a real and common fault.
- If it settles on five, that is Watchguard after failed ignition retries.
- The stored error history is more reliable than counting: this control keeps the last ten codes even through a power cut.
How to fix it
- Nothing to fix on a six-flash reading. Recount first.
- Better still, read the stored error history rather than counting live — it removes the counting problem entirely.
- Once the real count is established, follow the page for that code.
Notes
Worth knowing that a manufacturer skipping a number in a sequence is normal rather than an omission in this site's coverage. ICP does the same with one flash on its SmartValve control.
Related
- Error code recall — The last ten faults, retained even through a power cut
- 7 flashes — Primary or secondary limit open, or Watchguard after three minutes open
All codes for this manufacturer
Armstrong Air, AirEase, Concord and Ducane furnace codes — every code, with what differs between models.
Not sure this is your brand?
The same count means something else on other furnaces. What 6 flashes means on every brand puts them side by side.
What the fix costs
Read correctly, this code costs nothing — there is no six-flash fault on the -02 control to repair. The cost worth avoiding is the $75–150 diagnostic visit (furnace repair cost guide) booked on a miscount, where the technician's first act is recounting the flashes you could have recounted yourself. Watch three full repetitions of the pattern before phoning anyone. If a real code emerges from the recount, the price conversation belongs on that code's page, because seven flashes and five flashes lead to very different bills.
Do it yourself or call someone?
Counting flashes is exactly the kind of work a homeowner should do, and this control offers a better tool than the live LED: the error recall function replays the last ten stored codes one at a time, which removes the counting-mid-pattern problem entirely. If recall shows a real code, follow that page. If the LED is doing something no count explains — erratic, dim, flickering — that is control-board behaviour rather than a code, and worth a professional look rather than a guess.
Unused counts on other controls
Allied is not alone in leaving a number empty: the ICP SmartValve table assigns no meaning to a single flash either, and an unassigned count works the same way on both — as a built-in miscount detector. Why the same count means different things across brands is covered in same code, different meanings.
What this looks like
From the outside, this usually shows up as there is no heat but nothing looks obviously wrong — that walkthrough covers what to check in order, and when it stops being a homeowner job.