Goodman furnace 3 amber flashes: Second stage heat called with no first stage call
Three amber flashes means the thermostat is calling for second stage heat without calling for first stage. That is not a valid combination, and it points at the thermostat or its wiring.
Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.
What it means
A two-stage furnace expects its thermostat to call for first stage heat and then, if more output is needed, add second stage on top. A second stage call arriving without a first stage call is not a sequence the furnace can act on, so the control flags it. This is a wiring or configuration fault rather than a mechanical one: the furnace is working correctly and reporting that it has been given contradictory instructions. It appears most often after a thermostat has been replaced, particularly where a single-stage or incorrectly configured thermostat has been fitted to a two-stage furnace.
Most common causes
- A thermostat wired incorrectly, with the second stage heat wire connected but not the first.
- A single-stage thermostat fitted to a two-stage furnace and wired to the second stage terminal.
- A thermostat configured for the wrong equipment type.
- A broken or disconnected first stage heat wire, so only the second stage call arrives.
- A zone control board sending stage calls in the wrong order.
- A smart thermostat set up without specifying two-stage heating.
How to diagnose it
- Establish whether the thermostat has been replaced or reconfigured recently. This code following a thermostat change is the usual story.
- Confirm the colour is amber and not red. Note that amber is not a guarantee of normal operation on this control — this code and the four amber flash code are both faults, even though one and two amber flashes are normal heating.
- Note whether the furnace heats at all, and whether it seems to run only at full output.
- Check whether the thermostat is configured for two-stage heating in its own settings menu.
How to fix it
- Have the thermostat wiring checked against the furnace's terminals. This is the most common cause and is quickly resolved.
- Configure the thermostat for two-stage heating if it supports it, or fit one that does.
- If a wire has broken between the thermostat and the furnace, that needs tracing — technician work, though not an alarming fault.
- If a thermostat was recently installed, call whoever installed it. This is a configuration error rather than a furnace fault.
Notes
Two-stage furnaces fitted with thermostats that do not understand staging are common, and the furnace often appears to work — it simply never uses its low stage, which is where its efficiency advantage lives. This code catches that.
Related
- 4 amber flashes — Cooling called with no fan call
- 1 amber flash — Normal operation — first stage heat
All codes for this manufacturer
Goodman and Amana furnace fault codes — every code, with what differs between models.
Not sure this is your brand?
The same count means something else on other furnaces. What 3 flashes means on every brand puts them side by side.
Models this code appears on
From the manufacturer's per-model database. If your model is not listed, this code may not exist on your board, or it may mean something different — check the model page.
What the fix costs
For what a technician visit and this kind of repair typically runs, see the furnace repair cost guide.
What this looks like
From the outside, this usually shows up as there is no heat but nothing looks obviously wrong — that walkthrough covers what to check in order, and when it stops being a homeowner job.