Goodman furnace rapid green flashing: Normal operation — fan only, no heating or cooling

A rapidly flashing green LED means the blower is running on a fan call alone — the thermostat fan switch set to ON, with no heating or cooling demand.

Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED, running the blower on a fan-only call.

What it means

This is the indication for continuous fan. The thermostat is asking for air circulation with the G terminal energised and nothing else, so the furnace runs the blower and neither burns gas nor supports a cooling call. People set the fan to ON deliberately for air filtration or to even out temperatures between rooms, and then find the furnace running constantly and assume something has failed. This code is the answer to that. It is worth reading alongside the other rapid indications on this board, because rapid flashing in a different colour is not benign at all: rapid red is a twinning error, and rapid amber is low flame sense current. The speed is the same. The colour is the entire message.

Most common causes

The thermostat fan setting is on ON rather than AUTO.
A ventilation or air quality system calling for continuous circulation.
A zoning or fresh air control energising the fan independently.
A thermostat wiring fault holding G energised, which is the one cause here that is not intentional.

How to diagnose it

Check the thermostat fan setting first. If it is on ON, that is the whole explanation.
Confirm the flashing is green rather than red or amber — the other two rapid indications on this board are real faults.
If the fan setting is AUTO and the blower still runs continuously with this indication, the G circuit is being energised by something, and that is worth a technician tracing.
Note that continuous fan raises electricity use noticeably on an older PSC blower motor, less so on a variable speed one.

How to fix it

Set the thermostat fan to AUTO if continuous circulation was not intended.
If it was intended, nothing needs doing — this is the correct indication for it.
If AUTO does not stop it, the thermostat or its wiring is holding the fan call, and that is technician work.

Notes

Rapid flashing is used three times on this board with three different colours and three unrelated meanings. Anyone reporting a rapid flash without stating the colour has given no information at all.

All codes for this manufacturer

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

Sources

Goodman Manufacturing — Diagnostic Code Identification System (model-specific fault code lookup)

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.