Goodman Error Code CoreSense 9: Red 9 flashes – PROT output overcurrent (AC)

Updated October 13, 2026 · by Aurora Star Tech Inc.

Goodman error code CoreSense 9 on a air conditioner means: Red 9 flashes - PROT output overcurrent. It is also called Goodman diagnostic code CoreSense 9.

High severityAir ConditionerAlso Heat PumpGoodman/Amana R-32 GLXS/ALXS · Goodman/Amana R-410A GSX/ASX/DSX (ANX/SSX/VSX)

Homeowner? What Goodman code CoreSense 9 means for you

Call a technician Your air conditioner is reporting: Red 9 flashes - PROT output overcurrent. The air conditioner has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.

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.
Check both breakers and the outdoor disconnect box beside the outdoor unit; all should be ON.
Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
Keep about 2 feet around the outdoor unit clear of leaves, grass and debris.
If you see ice on the pipes or the indoor coil, turn the system off and run only the fan for a few hours, then call a technician.
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 CoreSense 9 mean?

The module saw more than 2 A on its PROT (protection output) terminal for 40 ms and shut the output off. The manual gives only this definition.

Applies to: Copeland CoreSense 3-wire module: Amana/Deluxe R-410A ASX, ASZ, DSX, DSZ units and Amana R-32 ALXS / ALZS units

Common causes of Goodman code CoreSense 9

Overload or short on the circuit fed by the PROT terminal (manual gives no further causes)

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 CoreSense 9

Show all 150 models

ALXS3BN**10AA ALXS4BA**10AA ALXS4NA**10AA ALXS5BA**10AA ANX130181 ANX130241 ANX130301 ANX130361 ANX130421 ANX130481 ANX130601 ANX130611 ANX140181 ANX140191 ANX140241 ANX140251 ANX140301 ANX140361 ANX140371 ANX140421 ANX140431 ANX140481 ANX140601 ASX180**1AB ASX130181 ASX130241 ASX130301 ASX130361 ASX130421 ASX130481 ASX130601 ASX130611 ASX140181 ASX140191 ASX140241 ASX140251 ASX140301 ASX140311 ASX140361 ASX140371 ASX140421 ASX140431 ASX140481 ASX140601 ASX160181 ASX160241 ASX160301 ASX160311 ASX160361 ASX160371 ASX160421 ASX160481 ASX160601 ASX160611 ASXH5***10 DSX160241 DSX160361 GLXS3BN**10AA GLXS4BA**10AA GLXS4MA**10AA GLXS5BA**10AA GSX16A181 GSX16A241 GSX16A301 GSX16A361 GSX16A421 GSX16A481 GSX16A601 GSX16S181 GSX16S241 GSX16S301 GSX16S361 GSX16S421 GSX16S481 GSX110903 GSX110904 GSX111203 GSX111204 GSX130181 GSX130241 GSX130301 GSX130361 GSX130363 GSX130371 GSX130421 GSX130481 GSX130483 GSX130484 GSX130601 GSX130603 GSX130604 GSX130611 GSX140181 GSX140191 GSX140241 GSX140251 GSX140301 GSX140311 GSX140361 GSX140371 GSX140421 GSX140431 GSX140481 GSX140601 GSX160181 GSX160241 GSX160301 GSX160311 GSX160361 GSX160371 GSX160421 GSX160481 GSX160601 GSX160611 GSXH5***10 SSX140181 SSX140241 SSX140301 SSX140361 SSX140421 SSX140481 SSX140601 SSX160241 SSX160301 SSX160361 SSX160421 SSX160481 SSX160591 SSX160601 VSX130181 VSX130241 VSX130301 VSX130361 VSX130371 VSX130421 VSX130481 VSX130601 VSX130611 VSX140181 VSX140191 VSX140241 VSX140251 VSX140301 VSX140311 VSX140361 VSX140371 VSX140421 VSX140431 VSX140481 VSX140601

Other Goodman AC codes

Code	Meaning
Comfort Alert TRIP+ALERT	TRIP and ALERT LEDs flashing together - control voltage too low
CoreSense 1	Yellow 1 flash - long run time (low side)
CoreSense 2	Pressure trip - yellow 2 flashes (red 2 = lockout)
CoreSense 3	Short cycling / pressure switch cycling - yellow 3 (red 3 = lockout)
CoreSense 4	Locked rotor - yellow 4 (red 4 = lockout)
CoreSense 5	Moderate run trip - yellow 5 (red 5 = lockout)
CoreSense solid red	Solid red TRIP - call present but compressor not running
d0	No shared data on the network
d1	Invalid shared data on the network
d2	System mismatch - indoor unit cannot supply required airflow
d3	Configuration mismatch - shared data does not match hardware
d4	Shared data from the loader rejected

All Goodman Air Conditioner error codes →

Goodman code CoreSense 9: homeowner questions

What does Goodman code CoreSense 9 mean?

Red 9 flashes - PROT output overcurrent. The module saw more than 2 A on its PROT (protection output) terminal for 40 ms and shut the output off. The manual gives only this definition.

Is it safe to keep using my air conditioner with code CoreSense 9?

It depends on the cause. The air conditioner has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.

Can I reset Goodman code CoreSense 9 myself?

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

Who can fix Goodman code CoreSense 9 near me?

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

Homeowner help: AC Running But Not Cooling: What to Check

Troubleshooting guides

Not cooling All brands · Air Conditioner
No cooling - R-32 GLXS/ALXS condenser Goodman · Air Conditioner

Source: Goodman RS6200301 R-32 GLXS/ALXS/GLZS/ALZS service (07-2024), CoreSense Diagnostics Table p.21-22 and Quick Reference Table p.23; Goodman RS6200006r103 R-410A ASX/GSX/DSX/ASZ/GSZ/DSZ service (text export) (Goodman_R_410A_ASX_GSX_DSX_A_C_and_ASZ_GSZ_DSZ_HP_covers_GSX_GSZ_lines_GSXH5_GSZH5_service.txt section Diagnostics Table: Coresense Module / Table 1 Quick Reference). 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.