Goodman furnace 1 red flash: Flame sensed when no flame should be present

One red flash means the control is detecting flame while the gas valve should be closed. Either gas is burning when it should not be, or the sensing circuit is reporting a flame that is not there.

Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces, which use a three-colour diagnostic LED. Red always indicates a fault. Green indicates cooling or standby. Amber is mostly heating status but not exclusively — rapid amber is a low flame sense warning, and three and four amber flashes are thermostat wiring faults. The colour must be read along with the count.

What it means

The GMEC96 control uses colour as well as flash count, and red is reserved for faults. One red flash means flame was proved at a moment when the gas valve was commanded shut. This is treated as serious because one of the two possible causes is a gas valve that is not closing fully — gas entering the combustion chamber outside a controlled cycle. The other cause is electrical: a short in the flame sensor wiring produces a signal the control cannot tell apart from a real flame. Since it cannot distinguish them, it assumes the dangerous one, which is correct behaviour for a control managing a gas appliance.

Most common causes

A gas valve leaking through or not closing fully, leaving a small flame after the cycle ends.
A slow-closing gas valve, where flame lingers briefly after shutdown.
A short to ground in the flame sensor wiring or at the sensor itself.
A chafed or damaged sensor wire touching the cabinet.
A failed control board misreading the flame signal.
Residual flame on a burner after the main flame is cut.

How to diagnose it

Confirm the colour is red and not amber. One amber flash on this control is normal first-stage heating, which is the opposite of a fault.
Note whether the inducer runs continuously without the furnace heating, which is the control purging the heat exchanger.
Do not open the burner compartment while the furnace is powered.
Note any smell of gas — if there is one, act on the fix below immediately rather than continuing to diagnose.

How to fix it

If you smell gas: leave the building, operate no electrical switches, and call your gas utility's emergency line or the fire service from outside. Do not return to investigate.
With no gas smell, switch the furnace off at its service switch and leave it off until a licensed technician has seen it.
This is entirely technician work, involving the gas valve and the flame-sensing circuit.
Do not reset repeatedly to see whether it clears. If a valve is passing gas, each reset is another opportunity for it to accumulate.

Notes

On this control the colour carries as much information as the count. One flash means a fault in red, normal first-stage heating in amber, and normal low-stage cooling in green — three completely different situations sharing one count.

Sources

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.