Goodman Error Code 1AC: Cooling, low stage (Furnace)

Updated October 15, 2026 · by Aurora Star Tech Inc.

Goodman error code 1AC on a furnace means: Cooling, low stage. It is also called Goodman diagnostic code 1AC.

Low severityFurnaceGoodman/Amana GM9S96/AM9S96 · Goodman/Amana GM9S80/AM9S80 · Goodman/Amana GM9C96/AM9C96

Homeowner? What Goodman code 1AC means for you

Usually minor Your furnace is reporting: Cooling, low stage. This code is usually informational or minor. The safe checks below often clear it; call us if it keeps showing up.

Safe things you can check yourself

Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
Make sure the furnace front door or panel is closed properly; many furnaces will not run with the door switch open.
Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
Check that the gas valve next to the furnace is open (handle in line with the pipe). Do not force it.
Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.

Call (647) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Goodman error code 1AC mean?

Shown during a low-stage cooling call (Y or Y1 from the thermostat). The compressor and condenser fan are running and the circulator starts at low cool speed after the cool-on delay (7 seconds by default). Normal operation; the single-stage models list the same status.

Applies to: GM9S96/AM9S96, GM9S80/AM9S80 and GM9C96/AM9C96 furnaces (7-segment control)

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

Goodman models that use code 1AC

Show all 80 models

AC9C96 AC9S800403AN AC9S800603AN AC9S800804BN AC9S800805CN AC9S801005CN AC9S960403BN AC9S960603BN AC9S960804CN AC9S961005CN AC9S961205CN AC9S961205DN AM9C96 AM9C960303AN AM9S800403AN AM9S800603AN AM9S800603BN AM9S800604BN AM9S800803BN AM9S800804BN AM9S800804CN AM9S800805CN AM9S801005CN AM9S801205DN AM9S920403AN AM9S920603BN AM9S920803BN AM9S920804CN AM9S920805CN AM9S921004CN AM9S921005CN AM9S921205DN AM9S960403AN AM9S960603BN AM9S960803BN AM9S960804CN AM9S960805CN AM9S961004CN AM9S961005CN AM9S961205DN GC9C96 GC9S800403AN GC9S800603AN GC9S800804BN GC9S800805CN GC9S801005CN GC9S960403BN GC9S960603BN GC9S960804CN GC9S961005CN GC9S961205CN GC9S961205DN GM9C96 GM9C960303AN GM9S800403AN GM9S800603AN GM9S800603BN GM9S800604BN GM9S800803BN GM9S800804BN GM9S800804CN GM9S800805CN GM9S801005CN GM9S801205DN GM9S920403AN GM9S920603BN GM9S920803BN GM9S920804CN GM9S920805CN GM9S921004CN GM9S921005CN GM9S921205DN GM9S960403AN GM9S960603BN GM9S960803BN GM9S960804CN GM9S960805CN GM9S961004CN GM9S961005CN GM9S961205DN

Other Goodman Furnace codes

Code	Meaning
2AC	Cooling, high stage
Cr	Code release number
E10	Grounding fault / poor neutral connection
E11	Flame rollout switch open
EE0	Lockout - too many ignition retries (3)
EE1	Pressure switch closed at start of heating cycle
EE2	Pressure switch did not close (inducer runs, no ignition)
EE3	High (primary) limit open
EE4	Flame sensed with no call for heat
EE5	Open fuse (short in low voltage wiring)
EE6	Low flame signal
EE8	High-stage pressure switch closed at start of heating cycle

All Goodman Furnace error codes →

Goodman code 1AC: homeowner questions

What does Goodman code 1AC mean?

Cooling, low stage. Shown during a low-stage cooling call (Y or Y1 from the thermostat). The compressor and condenser fan are running and the circulator starts at low cool speed after the cool-on delay (7 seconds by default). Normal operation; the…

Is it safe to keep using my furnace with code 1AC?

Usually yes. Code 1AC is normally minor, but if it keeps coming back have it checked.

Can I reset Goodman code 1AC myself?

You can try one reset (power off for 30 seconds, then on). If Goodman code 1AC comes back, the cause is still there and a licensed technician should check it.

Who can fix Goodman code 1AC near me?

Aurora Star Tech Inc. repairs Goodman furnaces in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: Furnace Not Turning On: What to Check · Furnace Blinking Light: What the Flash Codes Mean

Troubleshooting guides

Blowing cold air All brands · Furnace
No heat All brands · Furnace
Short cycling All brands · Furnace
Control display blank, furnace dead - Goodman/Amana 9-speed ECM furnaces Goodman · Furnace
No heat - Goodman/Amana 9-speed ECM furnaces Goodman · Furnace
Poor combustion / flame problems - Goodman/Amana GM9C96 Goodman · Furnace
Reset the furnace control to factory defaults (rFd) Goodman · Furnace
View and clear the last 6 stored faults (L6F) Goodman · Furnace

Source: GM9S96 service RS6612022r1, 1 Stage Status Codes - Status Menu p.28; GM9S80 service RS6621008r2, Status Menu p.31; GM9C96 service RS6612020r1, 2 Stage Status Codes p.34. Written in our own words as a summary; always check the original manual.

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.