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Goodman Error Code 9 flashes: Twinning fault (Furnace)

Updated · by Aurora Star Tech Inc.

Goodman error code 9 flashes on a furnace means: Twinning fault. It is also called Goodman diagnostic code 9 flashes.

Medium severityFurnaceGoodman/Amana *MES9 single-stage

Homeowner? What Goodman code 9 flashes means for you

Check, then call Your furnace is reporting: Twinning fault. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.

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) 657-2977Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does Goodman error code 9 flashes mean?

Problem with twinned furnaces. Blowers do not run together and no blower runs. This code is not stored in memory.

Applies to: GMES9, GCES9, AMES9, ACES9, VMES9, VCES9 (single stage, 92% and 96%)

Common causes of Goodman code 9 flashes

  • Twin terminals not wired together in the field
  • Isolating relay missing or installed wrong
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 9 flashes

Show all 57 models

ACES96ACES960403BNAAACES960603BNAAACES960804CNAAACES961005CNAAACES961205DNAAAMES92AMES96AMES920403ANAAAMES920603BNAAAMES920803BNAAAMES920804CNAAAMES920805CNAAAMES921004CNAAAMES921005CNAAAMES921205DNAAAMES960403ANAAAMES960603BNAAAMES960803BNAAAMES960804CNAAAMES960805CNAAAMES961005CNAAAMES961205DNAAGCES96GCES960403BNAAGCES960603BNAAGCES960804CNAAGCES961005CNAAGCES961205DNAAGMES92GMES96GMES920403ANAAGMES920603BNAAGMES920803BNAAGMES920804CNAAGMES920805CNAAGMES921004CNAAGMES921005CNAAGMES921205DNAAGMES960403ANAAGMES960603BNAAGMES960803BNAAGMES960804CNAAGMES960805CNAAGMES961005CNAAGMES961205DNAAVCES96VCES960403BNAAVCES960603BNAAVCES960804CNAAVCES961005CNAAVMES96VMES960403ANAAVMES960603BNAAVMES960803BNAAVMES960804CNAAVMES961005CNAA

Other Goodman Furnace codes

CodeMeaning
3 flashesPressure switch stuck open
4 flashesPrimary or auxiliary limit open
5 flashesFlame sensed with no call for heat
6 flashesRollout limit open or control fuse blown
7 flashesLow flame signal
8 flashesIgniter relay fault
10 flashesOpen fuse - no 24 V at the control
11 flashesIgniter open
12 flashesInducer relay fault
88Power-up self check
ACCooling, single stage
AC1Cooling, low stage (communicating)

All Goodman Furnace error codes →

Goodman code 9 flashes: homeowner questions

What does Goodman code 9 flashes mean?

Twinning fault. Problem with twinned furnaces. Blowers do not run together and no blower runs. This code is not stored in memory.

Is it safe to keep using my furnace with code 9 flashes?

It depends on the cause. This is often caused by something simple. Try the safe checks below; if the code returns, book a service call before it turns into a no-heat or no-hot-water emergency.

Can I reset Goodman code 9 flashes myself?

You can try one reset (power off for 30 seconds, then on). If Goodman code 9 flashes comes back, the cause is still there and a licensed technician should check it.

Who can fix Goodman code 9 flashes 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

Source: Goodman Service and Troubleshooting GMES9*/GCES9*/AMES9*/ACES9*/VMES9*/VCES9* (RS6612016r3) , Troubleshooting Chart p.52; LED table p.44. 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.

© 2026 Aurora Star Tech Inc. All rights reserved. This page may not be copied, republished or used to train other systems without written permission.

Emergency Furnace Repair

647-657-2977