Goodman furnace 8 red flashes: External lockout — recycles exhausted
Eight red flashes means flame was established and then lost, repeatedly, until the control ran out of recycles. The furnace can light — it cannot keep the flame.
Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.
What it means
A recycle is a restart after a flame was proved and subsequently lost, as distinct from a retry where the flame never lit. This code means the furnace has been through its allowed recycles and stopped. That is a meaningfully different fault from a retry lockout: the igniter works, the gas valve opens, and a flame forms. Something then either extinguishes the flame or stops the control being able to detect it. The most common single cause is a flame sensor whose signal is falling — the flame is still there, and the control can no longer see it well enough to keep the valve open.
Most common causes
- A flame sensor coated with oxide, giving a signal that fades within seconds of lighting.
- The flame sensor bent or shifted so it sits only partly in the flame.
- Poor grounding, which makes flame rectification unreliable.
- Low or unstable gas pressure, so the flame lights and cannot be sustained.
- Restricted combustion air, producing a flame that lifts or destabilises.
- A partly blocked flue disturbing the flame once combustion is established.
- A cracked ceramic insulator on the flame sensor leaking the signal to the cabinet.
How to diagnose it
- Confirm this is eight and not seven flashes, since the two point at different failures.
- Watch a start attempt if the furnace has a sight glass. Burners lighting and going out after a few seconds is the signature of this code.
- Note how long the flame survives. A few seconds points strongly at flame sensing; longer points at gas pressure or combustion air.
- Check when the furnace was last serviced, since an uncleaned flame sensor is the usual explanation.
How to fix it
- Flame sensor cleaning, grounding checks, and gas pressure testing are technician work.
- Tell the technician that the burners do light and then go out. It is the single most useful observation for this fault and it rules out the igniter immediately.
- Do not reset repeatedly. Each cycle delivers gas that briefly burns and then stops.
- If the sensor has been cleaned recently and the fault has returned, ask for grounding to be checked rather than the sensor cleaned again.
Notes
A furnace that lights, burns for a few seconds, then shuts down and eventually locks out is the classic dirty flame sensor. It is among the most common furnace faults and one of the least expensive repairs — but it sits in the flame-sensing circuit and is technician work.
Related
- 7 red flashes — External lockout — ignition retries exhausted
- rapid amber flashing — Low flame sense current
All codes for this manufacturer
Goodman and Amana furnace fault codes — every code, with what differs between models.
Not sure this is your brand?
The same count means something else on other furnaces. What 8 flashes means on every brand puts them side by side.
Models this code appears on
From the manufacturer's per-model database. If your model is not listed, this code may not exist on your board, or it may mean something different — check the model page.
The same fault on other control families
Recycles exhausted is the subtler sibling of the seven-flash lockout, and the distinction is preserved across the shared table: York's eight red flashes defines it identically. Where seven red means the furnace never lit, eight means it lit every time and could not keep the flame — which shifts suspicion from the ignition side to everything that sustains a burn: flame sensing, gas supply stability, and venting. That difference is exactly the information a technician wants before arriving, and this board hands it to you for free.
What the fix costs
The cheapest and most common outcome is the classic one: a flame sensor too dirty to prove the flame it is standing in, cleaned for $80–200 — the repair cost guide calls it the ten-minute job. From there the branches climb: an unstable draft snuffing flames mid-cycle is pressure-switch-and-venting territory at $150–400, a faltering inducer $300–900, and gas supply problems land wherever the utility or the piping does. The good news hiding in this code is diagnostic rather than financial: a furnace that lights reliably has already exonerated its ignitor, so nobody should be quoting you ignition parts without explaining why.
DIY or call a pro?
If the burner compartment has a sight glass, the safe homeowner observation is watching one attempt: flames that light cleanly and die seconds later confirm the pattern this code describes. That is where DIY ends. The flame sensing circuit is on this site's hard professional list, venting diagnosis needs instruments, and the failure mode itself — repeated light-and-lose cycles — is not one to keep feeding with resets. One reset after a suspected one-off (a pressure blip on a wild night, say) is reasonable; a second lockout in short order means stop and book. Mention whether the flames look lazy or lift off the burner; it is the kind of detail that shortcuts a diagnosis.
What this looks like
From the outside, this usually shows up as the vents blowing cold air on a heat call — that walkthrough covers what to check in order, and when it stops being a homeowner job.