Goodman furnace solid green: Standby — powered, no call
A steady green light means the furnace is powered, healthy, and waiting. If the house is cold and the light is solid green, the furnace has not been asked to run.
Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.
What it means
Green on this control indicates cooling and standby states, and a steady green is the idle indication: powered, no faults, no call. That is genuinely informative when the house is cold, because it narrows the search considerably — the furnace has power, its safety circuits are satisfied, and it has no stored fault. It simply has not been asked to do anything. The request comes from the thermostat over the low voltage wiring, so a cold house with a solid green light points at the thermostat, its wiring, or its power rather than at the furnace itself.
Most common causes
- The furnace is idle and everything is normal.
- The thermostat is not calling for heat — set to cool, set to off, or set below room temperature.
- The thermostat's batteries are flat.
- A break in the low voltage wiring between the thermostat and the furnace.
- A thermostat that has failed or lost its programming.
- A thermostat wired incorrectly after replacement.
- A zone control board not passing the call through.
How to diagnose it
- Check the thermostat is set to heat and above the current room temperature.
- Replace the thermostat batteries if it takes them, even if the display looks normal.
- Note whether the thermostat shows a call-for-heat indicator. A thermostat that thinks it is calling and a furnace showing standby means the signal is not arriving.
- Check whether the blower runs on the fan-on setting. Fan working and heat not points at the heat wire.
- Note whether the fault followed a thermostat replacement, since miswiring produces exactly this.
How to fix it
- Correct the thermostat setting or replace its batteries.
- If a thermostat was recently changed, have the wiring checked against the furnace terminals. Smart thermostat installations without a common wire are a frequent source of no-heat calls.
- Low voltage wiring faults and zone control problems are technician work, though they are among the less alarming findings.
- If the furnace is heating normally, nothing needs doing.
Notes
Knowing what your own furnace shows when idle is worth the minute it takes to look. A solid green light means nothing useful if you do not know it was solid green last week too.