SplitAtlas

Error-code hub

MRCOOL error codes

MRCOOL indoor units show the code on the head's display, and the outdoor board reports its own separate set - which is why some codes here begin EC, PC or LC rather than E or F. The 44 codes below come from MRCOOL service manuals. Because MRCOOL DIY systems use quick-connect line sets, several faults that would be refrigerant work on other brands are connection issues here - worth checking first.

See MRCOOL mini-splits ->Common FirstStatus DisplaysError Codes
Status displays
6
Error codes
44

Unit applicability

Match your unit before reading the table

MRCOOL code meanings vary by generation and unit family. This hub is sourced for DIY 5th Generation; if your unit is Gen 1-4, a different DIY generation, multi-zone, or another MRCOOL line, confirm against that unit's own manual before using the table.

DIY 5th Generation5 models

Common codes first

Most broadly applicable documented codes

Ranking basis: we do not have failure-frequency telemetry. These are ordered by breadth of affected systems in the SplitAtlas catalog - the documented product line's published model count, whether the same code appears on more than one product line, and any manual applicability notes we hold. This is a breadth ranking, not a popularity claim.

EC 54

EC 54 means compressor discharge temperature sensor TP sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Breadth evidence
5 published catalog models on its documented product line. Manual applicability notes: MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.; For certain models the outdoor unit uses a combination sensor where T3, T4, and TP are the same sensor.
Safe first check
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
View the fix
PC 06

PC 06 means compressor discharge temperature exceeds the manual's threshold for 9 seconds; the compressor stops and the LED displays the fault code. The manual trigger fits the compressor or refrigerant-circuit protection category.

AdvisoryTechnician
Breadth evidence
5 published catalog models on its documented product line. Manual applicability notes: MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.; For certain models the outdoor unit uses a combination sensor where T3, T4, and TP are the same sensor.
Safe first check
Clean the indoor filter, clear vegetation or snow around the outdoor unit, and leave refrigerant, valves, gauges, and leak repair to a licensed technician. If the code returns, write down the exact display and stop there.
View the fix
EC 07

EC 07 means outdoor fan speed stays too low or too high for the manual's detection time; the outdoor LED displays the failure code and the system turns off. The manual trigger fits the outdoor fan category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Breadth evidence
5 published catalog models on its documented product line. Manual applicability notes: MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.
Safe first check
Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.
View the fix
EC 51

EC 51 means the outdoor PCB main chip does not receive feedback from the outdoor EEPROM chip. The manual trigger fits the control-board category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Breadth evidence
5 published catalog models on its documented product line. Manual applicability notes: MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.
Safe first check
Note whether the code appeared after a storm, outage, generator use, or recent service. Do not open the control compartment. If the code returns, write down the exact display and stop there.
View the fix
EC 52

EC 52 means outdoor coil temperature sensor T3 sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Breadth evidence
5 published catalog models on its documented product line. Manual applicability notes: MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.
Safe first check
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
View the fix
EC 53

EC 53 means outdoor ambient temperature sensor T4 sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Breadth evidence
5 published catalog models on its documented product line. Manual applicability notes: MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.
Safe first check
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
View the fix

Safe first checks

Checks you can do without opening the unit

These codes have homeowner-safe steps such as filters, airflow, condensate/drain checks, remote/controller items, or a single safe power reset. If the code returns, stop at the boundary in the card.

EC 07Technician

Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.

Read the full code guide
EC 71Technician

Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.

Read the full code guide
EC 72Technician

Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.

Read the full code guide
EH 03Technician

Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.

Read the full code guide

MRCOOL mini-splits

Use the MRCOOL catalog to connect these manual error codes to current model pages and replacement options.

See MRCOOL mini-splits ->

Status displays

DF

Defrost cycle running

Not an error
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
None - normal, especially in cold weather
Status note
This is a normal status indication, not an error, unless comfort is poor or the status never clears.
View the fix ->

CL

Active Clean function

Not an error
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
None - normal
Status note
This is a normal status indication, not an error, unless comfort is poor or the status never clears.
View the fix ->

FP

Room-freeze protection heating (<46.4F)

Not an error
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
None - normal
Status note
This is a normal status indication, not an error, unless comfort is poor or the status never clears.
View the fix ->

FC

Forced cooling mode

Not an error
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Exit via remote if unintended
Status note
This is a normal status indication, not an error, unless comfort is poor or the status never clears.
View the fix ->

AP

Wi-Fi AP pairing mode

Not an error
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Complete or exit app pairing
Status note
This is a normal status indication, not an error, unless comfort is poor or the status never clears.
View the fix ->

CP

Remote switched off

Not an error
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Check remote/switch setting
Status note
This is a normal status indication, not an error, unless comfort is poor or the status never clears.
View the fix ->

All error codes

EH C1

EH C1 means the refrigerant sensor detects leakage concentration at or above the manual's LFL thresholds. The manual trigger fits the refrigerant leak detection category. Follow the reset procedure below once; repeated resets are not a fix.

Stop useTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Shut the system down, ventilate the room, avoid ignition sources, and do not run normal heating or cooling until a licensed technician checks it. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH C1 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The refrigerant sensor detects leakage concentration at or above the manual's LFL thresholds" and point them to 4.7 TS06-N10: Refrigerant sensor detects leakage diagnosis and solution.
View the fix ->

EH C2

EH C2 means the refrigerant sensor is out of range and leakage is detected at the manual's LFL thresholds. The manual trigger fits the refrigerant leak detection category. Follow the reset procedure below once; repeated resets are not a fix.

Stop useTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Shut the system down, ventilate the room, avoid ignition sources, and do not run normal heating or cooling until a licensed technician checks it. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH C2 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The refrigerant sensor is out of range and leakage is detected at the manual's LFL thresholds" and point them to 4.7 TS06-N10: Refrigerant sensor detects leakage diagnosis and solution.
View the fix ->

EL 0C

EL 0C means the manual judges a refrigeration-system abnormality from compressor count and operating-parameter changes caused by excessive exhaust temperature. The manual trigger fits the refrigerant leak or low-charge category. Follow the reset procedure below once; repeated resets are not a fix.

Stop useTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Shut the system down, ventilate the room if a leak sensor is involved, avoid ignition sources, and do not run normal heating or cooling until a licensed technician checks it. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EL 0C returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The manual judges a refrigeration-system abnormality from compressor count and operating-parameter changes caused by excessive exhaust temperature" and point them to 4.7 TS06-INV: System lacks refrigerant diagnosis and solution.
View the fix ->

EC 07

EC 07 means outdoor fan speed stays too low or too high for the manual's detection time; the outdoor LED displays the failure code and the system turns off. The manual trigger fits the outdoor fan category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 07 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "Outdoor fan speed stays too low or too high for the manual's detection time; the outdoor LED displays the failure code and the system turns off" and point them to 4.7 TS04-ODU: Outdoor DC fan speed has been out of control diagnosis and solution.
View the fix ->

EC 51

EC 51 means the outdoor PCB main chip does not receive feedback from the outdoor EEPROM chip. The manual trigger fits the control-board category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Note whether the code appeared after a storm, outage, generator use, or recent service. Do not open the control compartment. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 51 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The outdoor PCB main chip does not receive feedback from the outdoor EEPROM chip" and point them to 4.7 TS01-ODU: Outdoor EEPROM parameter error diagnosis and solution.
View the fix ->

EC 52

EC 52 means outdoor coil temperature sensor T3 sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 52 remains or returns. Tell them the manual trigger is "Outdoor coil temperature sensor T3 sampling voltage is lower than 0.06V or higher than 4.94V" and point them to 4.7 TS05-ODU: Outdoor temperature sensor error diagnosis and solution.
View the fix ->

EC 53

EC 53 means outdoor ambient temperature sensor T4 sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 53 remains or returns. Tell them the manual trigger is "Outdoor ambient temperature sensor T4 sampling voltage is lower than 0.06V or higher than 4.94V" and point them to 4.7 TS05-ODU: Outdoor temperature sensor error diagnosis and solution.
View the fix ->

EC 54

EC 54 means compressor discharge temperature sensor TP sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 54 remains or returns. Tell them the manual trigger is "Compressor discharge temperature sensor TP sampling voltage is lower than 0.06V or higher than 4.94V" and point them to 4.7 TS05-ODU: Outdoor temperature sensor error diagnosis and solution.
View the fix ->

EC 71

EC 71 means over-current failure of the outdoor DC fan motor. The manual trigger fits the outdoor fan category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 71 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "Over-current failure of the outdoor DC fan motor" and point them to 4.3 Error Display; 4.7 TS04-ODU.
View the fix ->

EC 72

EC 72 means lack-phase failure of the outdoor DC fan motor; the manual describes abnormal three-phase sampling current, especially when one or more phase currents stay small and almost zero. The manual trigger fits the outdoor fan category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EC 72 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "Lack-phase failure of the outdoor DC fan motor; the manual describes abnormal three-phase sampling current, especially when one or more phase currents stay small and almost zero" and point them to 4.7 TS38: Lack of phase failure of ODU DC fan motor diagnosis and solution.
View the fix ->

EH 00

EH 00 means the indoor unit reports an EEPROM malfunction because the PCB main chip does not receive feedback from the EEPROM chip. The manual trigger fits the control-board category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Note whether the code appeared after a storm, outage, generator use, or recent service. Do not open the control compartment. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 00 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The indoor unit reports an EEPROM malfunction because the PCB main chip does not receive feedback from the EEPROM chip" and point them to 4.7 TS01-IDU: Indoor EEPROM parameter error diagnosis and solution.
View the fix ->

EH 02

EH 02 means the indoor PCB does not receive zero-crossing signal feedback for 4 minutes or the zero-crossing signal interval is abnormal. The manual trigger fits the zero-crossing signal circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Confirm the breaker is fully on and leave supply-wiring, fan-motor, and control-board checks to a licensed technician. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 02 remains or returns. Tell them the manual trigger is "The indoor PCB does not receive zero-crossing signal feedback for 4 minutes or the zero-crossing signal interval is abnormal" and point them to 4.7 TS03: Zero crossing signal detection error diagnosis and solution.
View the fix ->

EH 03

EH 03 means indoor fan speed stays too low or too high for the manual's detection time; the LED displays the failure code and the air conditioner turns off. The manual trigger fits the indoor fan category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn power off before looking at the fan area. From outside the cabinet only, clear loose leaves, snow, or obvious debris around the grille; do not reach through the guard. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 03 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "Indoor fan speed stays too low or too high for the manual's detection time; the LED displays the failure code and the air conditioner turns off" and point them to 4.7 TS04-S-IDU: Indoor fan speed has been out of control diagnosis and solution.
View the fix ->

EH 0A

EH 0A means the indoor unit reports an EEPROM parameter error. The manual trigger fits the control-board category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Note whether the code appeared after a storm, outage, generator use, or recent service. Do not open the control compartment. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 0A returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The indoor unit reports an EEPROM parameter error" and point them to 4.7 TS01-IDU: Indoor EEPROM parameter error diagnosis and solution.
View the fix ->

EH 0B

EH 0B means the indoor PCB does not receive feedback from the display board. The manual trigger fits the display-board communication category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Use the page's reset procedure once if one is documented. Do not open the electrical cabinet or move signal wiring. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 0B returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The indoor PCB does not receive feedback from the display board" and point them to 4.7 TS07: Indoor PCB/display board communication error diagnosis and solution.
View the fix ->

EH 60

EH 60 means indoor room temperature sensor T1 sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 60 remains or returns. Tell them the manual trigger is "Indoor room temperature sensor T1 sampling voltage is lower than 0.06V or higher than 4.94V" and point them to 4.7 TS05-IDU: Indoor temperature sensor error diagnosis and solution.
View the fix ->

EH 61

EH 61 means indoor pipe temperature sensor T2 sampling voltage is lower than 0.06V or higher than 4.94V. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH 61 remains or returns. Tell them the manual trigger is "Indoor pipe temperature sensor T2 sampling voltage is lower than 0.06V or higher than 4.94V" and point them to 4.7 TS05-IDU: Indoor temperature sensor error diagnosis and solution.
View the fix ->

EH C3

EH C3 means the refrigerant sensor is out of range. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EH C3 remains or returns. Tell them the manual trigger is "The refrigerant sensor is out of range" and point them to 4.7 TS05-N10: Refrigerant sensor error diagnosis and solution.
View the fix ->

EL 01

EL 01 means the indoor unit cannot communicate with the outdoor unit. The manual identifies the condition but does not tie it to a broader cause family. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Follow the documented reset procedure below once. Do not open the equipment or repeat the reset if the code returns. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if EL 01 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The indoor unit cannot communicate with the outdoor unit" and point them to 4.7 TS02-S-INV: Indoor unit and outdoor unit communication error diagnosis and solution.
View the fix ->

FH CC

FH CC means the indoor unit reports a refrigerant sensor error after receiving a fault signal or losing sensor feedback. The manual trigger fits the sensor, detector, or thermistor circuit category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Power cycle once only when the page includes a reset procedure, and make sure accessible air paths are not blocked. Do not open cabinets to test sensors or detectors. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if FH CC remains or returns. Tell them the manual trigger is "The indoor unit reports a refrigerant sensor error after receiving a fault signal or losing sensor feedback" and point them to 4.7 TS05-N10: Refrigerant sensor error diagnosis and solution.
View the fix ->

LC 06

LC 06 means the IPM module temperature is higher than the manual's protection value. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if LC 06 remains or returns. Tell them the manual trigger is "The IPM module temperature is higher than the manual's protection value" and point them to 4.7 TS11-S-INV: IPM module high temperature protection diagnosis and solution.
View the fix ->

PC 00

PC 00 means the voltage signal sent from the IPM to the compressor drive chip is abnormal. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 00 remains or returns. Tell them the manual trigger is "The voltage signal sent from the IPM to the compressor drive chip is abnormal" and point them to 4.7 TS09-S: IPM module protection diagnosis and solution.
View the fix ->

PC 01

PC 01 means the outdoor voltage detection circuit detects abnormal increases or decreases in voltage. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 01 remains or returns. Tell them the manual trigger is "The outdoor voltage detection circuit detects abnormal increases or decreases in voltage" and point them to 4.7 TS10-S: Over voltage or too low voltage protection diagnosis and solution.
View the fix ->

PC 02

PC 02 means the IPM module temperature is higher than the manual's protection value. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 02 remains or returns. Tell them the manual trigger is "The IPM module temperature is higher than the manual's protection value" and point them to 4.7 TS11-S-INV: IPM module high temperature protection diagnosis and solution.
View the fix ->

PC 03

PC 03 means low- or high-pressure protection; the high-pressure switch cuts off above 638 PSI/4.4MPa or the low-pressure switch cuts off below 18.85 PSI/0.13MPa. The manual trigger fits the compressor or refrigerant-circuit protection category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Clean the indoor filter, clear vegetation or snow around the outdoor unit, and leave refrigerant, valves, gauges, and leak repair to a licensed technician. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 03 remains or returns. Tell them the manual trigger is "Low- or high-pressure protection; the high-pressure switch cuts off above 638 PSI/4.4MPa or the low-pressure switch cuts off below 18.85 PSI/0.13MPa" and point them to 4.7 TS26-INV: High pressure or low pressure protection diagnosis and solution.
View the fix ->

PC 04

PC 04 means the manual describes abnormal inverter compressor drive involving communication signal, voltage, or compressor rotation-speed detection. The manual trigger fits the compressor-drive communication category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Use the page's reset procedure once if one is documented. Do not open the outdoor electrical cabinet or test the compressor drive. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 04 remains or returns. Tell them the manual trigger is "The manual describes abnormal inverter compressor drive involving communication signal, voltage, or compressor rotation-speed detection" and point them to 4.7 TS12-S: Inverter compressor drive error diagnosis and solution.
View the fix ->

PC 06

PC 06 means compressor discharge temperature exceeds the manual's threshold for 9 seconds; the compressor stops and the LED displays the fault code. The manual trigger fits the compressor or refrigerant-circuit protection category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Clean the indoor filter, clear vegetation or snow around the outdoor unit, and leave refrigerant, valves, gauges, and leak repair to a licensed technician. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 06 remains or returns. Tell them the manual trigger is "Compressor discharge temperature exceeds the manual's threshold for 9 seconds; the compressor stops and the LED displays the fault code" and point them to 4.7 TS32: Discharge temperature protection of compressor diagnosis and solution.
View the fix ->

PC 08

PC 08 means the current detection circuit detects an abnormal current rise. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 08 remains or returns. Tell them the manual trigger is "The current detection circuit detects an abnormal current rise" and point them to 4.7 TS08-S: Current overload protection diagnosis and solution.
View the fix ->

PC 0A

PC 0A means high condenser/outdoor pipe temperature protection. The manual trigger fits the compressor or refrigerant-circuit protection category. The self-clear note below explains when the display should clear; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Clean the indoor filter, clear vegetation or snow around the outdoor unit, and leave refrigerant, valves, gauges, and leak repair to a licensed technician. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 0A does not self-clear as described or returns. Tell them the manual trigger is "High condenser/outdoor pipe temperature protection" and point them to 4.7 TS27-INV: High temperature protection of condenser diagnosis and solution.
View the fix ->

PC 0F

PC 0F means the voltage signal that the IPM sends to the compressor drive chip is abnormal and the system turns off. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 0F remains or returns. Tell them the manual trigger is "The voltage signal that the IPM sends to the compressor drive chip is abnormal and the system turns off" and point them to 4.7 TS30: PFC module protection diagnosis and solution.
View the fix ->

PC 10

PC 10 means outdoor low AC voltage protection from the outdoor voltage detection circuit. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 10 remains or returns. Tell them the manual trigger is "Outdoor low AC voltage protection from the outdoor voltage detection circuit" and point them to 4.3 Error Display; 4.7 TS10-S.
View the fix ->

PC 11

PC 11 means outdoor main control board DC bus high voltage protection from the voltage detection circuit. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 11 remains or returns. Tell them the manual trigger is "Outdoor main control board DC bus high voltage protection from the voltage detection circuit" and point them to 4.3 Error Display; 4.7 TS10-S.
View the fix ->

PC 12

PC 12 means outdoor main control board DC bus low voltage protection / 341 MCE error from the voltage detection circuit. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 12 remains or returns. Tell them the manual trigger is "Outdoor main control board DC bus low voltage protection / 341 MCE error from the voltage detection circuit" and point them to 4.3 Error Display; 4.7 TS10-S.
View the fix ->

PC 30

PC 30 means system high pressure protection; the high-pressure switch cuts off the system above 638 PSI/4.4MPa. The manual trigger fits the compressor or refrigerant-circuit protection category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Clean the indoor filter, clear vegetation or snow around the outdoor unit, and leave refrigerant, valves, gauges, and leak repair to a licensed technician. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 30 remains or returns. Tell them the manual trigger is "System high pressure protection; the high-pressure switch cuts off the system above 638 PSI/4.4MPa" and point them to 4.7 TS26-INV: High pressure protection diagnosis and solution.
View the fix ->

PC 31

PC 31 means system low pressure protection; the low-pressure switch cuts off the system below 18.85 PSI/0.13MPa. The manual trigger fits the compressor or refrigerant-circuit protection category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Clean the indoor filter, clear vegetation or snow around the outdoor unit, and leave refrigerant, valves, gauges, and leak repair to a licensed technician. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 31 remains or returns. Tell them the manual trigger is "System low pressure protection; the low-pressure switch cuts off the system below 18.85 PSI/0.13MPa" and point them to 4.7 TS26-INV: Low pressure protection diagnosis and solution.
View the fix ->

PC 40

PC 40 means the main PCB cannot detect the IPM board / compressor-driven chip. The manual trigger fits the compressor-drive communication category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Use the page's reset procedure once if one is documented. Do not open the outdoor electrical cabinet or test the compressor drive. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 40 remains or returns. Tell them the manual trigger is "The main PCB cannot detect the IPM board / compressor-driven chip" and point them to 4.7 TS31: Communication error between outdoor main chip and compressor-driven chip.
View the fix ->

PC 43

PC 43 means compressor lack-phase protection; the manual describes abnormal three-phase sampling current, especially when one or more phase currents stay small and almost zero. The manual trigger fits the inverter, voltage, or compressor-drive category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 43 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "Compressor lack-phase protection; the manual describes abnormal three-phase sampling current, especially when one or more phase currents stay small and almost zero" and point them to 4.7 TS39: ODU compressor lack of phase protection diagnosis and solution.
View the fix ->

PC 44

PC 44 means outdoor zero-speed protection assigned by the manual to the current overload diagnostic. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 44 remains or returns. Tell them the manual trigger is "Outdoor zero-speed protection assigned by the manual to the current overload diagnostic" and point them to 4.3 Error Display; 4.7 TS08-S.
View the fix ->

PC 45

PC 45 means the outdoor IR chip detects its own parameter error when powered on. The manual trigger fits the inverter, voltage, or compressor-drive category. Follow the reset procedure below once; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 45 returns after the documented reset or the condition does not clear. Tell them the manual trigger is "The outdoor IR chip detects its own parameter error when powered on" and point them to 4.7 TS40: ODU IR chip drive failure diagnosis and solution.
View the fix ->

PC 46

PC 46 means compressor speed out of control assigned by the manual to the current overload diagnostic. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 46 remains or returns. Tell them the manual trigger is "Compressor speed out of control assigned by the manual to the current overload diagnostic" and point them to 4.3 Error Display; 4.7 TS08-S.
View the fix ->

PC 49

PC 49 means compressor overcurrent failure assigned by the manual to the current overload diagnostic. The manual trigger fits the inverter, voltage, or compressor-drive category.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Turn the system off for 2 minutes, note any storm, brownout, generator, or breaker event, then restore power once if the breaker is stable. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 49 remains or returns. Tell them the manual trigger is "Compressor overcurrent failure assigned by the manual to the current overload diagnostic" and point them to 4.3 Error Display; 4.7 TS08-S.
View the fix ->

PC 0L

PC 0L means low ambient temperature protection triggers when T4 is below the manual's compressor-on or compressor-off low-temperature thresholds for 10 seconds. The manual identifies the condition but does not tie it to a broader cause family. The self-clear note below explains when the display should clear; repeated resets are not a fix.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Use the self-clear guidance below and do not open the equipment while you wait for the documented condition to clear. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PC 0L does not self-clear as described or returns. Tell them the manual trigger is "Low ambient temperature protection triggers when T4 is below the manual's compressor-on or compressor-off low-temperature thresholds for 10 seconds" and point them to 4.7 LP: Low ambient temperature protection.
View the fix ->

PH 90

PH 90 means high temperature protection of the evaporator. The manual identifies the condition but does not tie it to a broader cause family.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Use only the homeowner steps documented on this page. Do not infer a reset or open the equipment when the manual does not provide one. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PH 90 remains or returns. Tell them the manual trigger is "High temperature protection of the evaporator" and point them to 4.3 Error Display (Outdoor Unit with Auxiliary Board).
View the fix ->

PH 91

PH 91 means low temperature protection of the evaporator. The manual identifies the condition but does not tie it to a broader cause family.

AdvisoryTechnician
Sourced Jul 2026
Applies to
DIY 5th Generation
Homeowner fix
Use only the homeowner steps documented on this page. Do not infer a reset or open the equipment when the manual does not provide one. If the code returns, write down the exact display and stop there.
When to call a pro
Call a licensed HVAC technician if PH 91 remains or returns. Tell them the manual trigger is "Low temperature protection of the evaporator" and point them to 4.3 Error Display (Outdoor Unit with Auxiliary Board).
View the fix ->