Goodman furnace 10 red flashes: Gas flow detected with a call for heat

Ten red flashes means the control has detected gas flow at a point in the heating sequence where it did not command it. This is a gas valve fault and needs a technician.

Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.

What it means

This code sits in the same family as the flame-detected-with-valve-closed fault, but it is specifically about gas flow during a call for heat rather than at rest. The control tracks what it has commanded the gas valve to do and compares that against what it observes. A mismatch means the valve is not behaving as instructed — most likely passing gas when it should not be, or opening at the wrong point in the sequence. Because the gas valve is the component that admits fuel, a control that cannot predict its behaviour cannot operate the furnace safely, so it stops.

Most common causes

A gas valve passing gas when it should be closed.
A gas valve opening at the wrong point in the sequence.
A miswired gas valve, most often after recent service.
A failed valve relay on the control board.
Wiring damage in the gas valve circuit.
A control board fault misreading the valve state.

How to diagnose it

Note any smell of gas. If there is one, act on the fix below immediately rather than continuing to diagnose.
Do not open the burner compartment while the furnace is powered.
Establish whether the furnace has been serviced recently, since a miswired valve does not develop on its own.
Note whether the inducer runs continuously, which some controls do to purge the heat exchanger.

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.
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 circuit.
Do not reset repeatedly. If the valve is passing gas, each reset is another opportunity for it to accumulate.

Notes

Goodman's service bulletin SF-042 covers gas valve diagnostics on two stage and communicating furnaces, including how the valve terminals are energised. It is worth a technician consulting it rather than working from general practice, since two-stage valve behaviour differs between model families.

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.