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
All codes for this manufacturer
Goodman and Amana furnace fault codes — every code, with what differs between models.