DF
Defrost cycle running
- Homeowner check
- None - normal, especially in cold weather
- Technician scope
- N/A (status display, not an error)
Error-code hub
MRCOOL error codes
DIY 5th Generation status displays are listed first, followed by manual-sourced error codes with safe homeowner checks and technician-only scope.
- Status displays
- 6
- Error codes
- 44
Status displays
Verified Jul 2026
CL
Active Clean function
- Homeowner check
- None - normal
- Technician scope
- N/A (status display, not an error)
FP
Room-freeze protection heating (<46.4F)
- Homeowner check
- None - normal
- Technician scope
- N/A (status display, not an error)
FC
Forced cooling mode
- Homeowner check
- Exit via remote if unintended
- Technician scope
- N/A (status display, not an error)
AP
Wi-Fi AP pairing mode
- Homeowner check
- Complete or exit app pairing
- Technician scope
- N/A (status display, not an error)
CP
Remote switched off
- Homeowner check
- Check remote/switch setting
- Technician scope
- N/A (status display, not an error)
Error codes
EH C1
Refrigerant sensor detects leakage
- Homeowner check
- Ventilate room, shut unit at breaker, call technician - R454B is A2L class
- Technician scope
- Refrigerant sensor, leak repair
EH C2
Refrigerant sensor detects leakage
- Homeowner check
- Ventilate room, shut unit at breaker, call technician - R454B is A2L class
- Technician scope
- Refrigerant sensor, leak repair
EL 0C
System lacks refrigerant
- Homeowner check
- NONE - shut down, call technician (possible leak)
- Technician scope
- Leak test, recharge, T2, additional refrigerant
EC 07
Outdoor fan speed out of control
- Homeowner check
- Power off; check outdoor fan obstruction
- Technician scope
- Outdoor fan motor, PCB
EC 51
Outdoor EEPROM/T3/T4/TP sensor errors
- Homeowner check
- Power cycle; clear debris around outdoor unit
- Technician scope
- Sensors, outdoor PCB
EC 52
Outdoor EEPROM/T3/T4/TP sensor errors
- Homeowner check
- Power cycle; clear debris around outdoor unit
- Technician scope
- Sensors, outdoor PCB
EC 53
Outdoor EEPROM/T3/T4/TP sensor errors
- Homeowner check
- Power cycle; clear debris around outdoor unit
- Technician scope
- Sensors, outdoor PCB
EC 54
Outdoor EEPROM/T3/T4/TP sensor errors
- Homeowner check
- Power cycle; clear debris around outdoor unit
- Technician scope
- Sensors, outdoor PCB
EC 71
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
EC 72
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
EH 00
Indoor EEPROM malfunction/parameter error
- Homeowner check
- Power cycle at breaker (5 min off)
- Technician scope
- Indoor PCB
EH 02
Zero-crossing signal detection error
- Homeowner check
- Power cycle
- Technician scope
- Indoor PCB
EH 03
Indoor fan speed out of control
- Homeowner check
- Power off; check filter/blower obstruction
- Technician scope
- Indoor fan motor, PCB
EH 0A
Indoor EEPROM malfunction/parameter error
- Homeowner check
- Power cycle at breaker (5 min off)
- Technician scope
- Indoor PCB
EH 0B
Main board-display comm error
- Homeowner check
- Power cycle
- Technician scope
- Display board, PCB
EH 60
Room temp sensor (T1) error
- Homeowner check
- Power cycle
- Technician scope
- T1 sensor, PCB
EH 61
Indoor coil temp sensor (T2) error
- Homeowner check
- Power cycle
- Technician scope
- T2 sensor, PCB
EH C3
Refrigerant sensor error/out of range
- Homeowner check
- Power cycle once
- Technician scope
- Refrigerant sensor, PCB
EL 01
Indoor-outdoor communication error
- Homeowner check
- Power cycle; verify breaker fully on
- Technician scope
- Comm wiring, PCBs (both), reactor
FH CC
Refrigerant sensor error/out of range
- Homeowner check
- Power cycle once
- Technician scope
- Refrigerant sensor, PCB
LC 06
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 00
Outdoor IPM module protection
- Homeowner check
- Power cycle
- Technician scope
- IPM board, compressor, outdoor PCB
PC 01
Voltage protection
- Homeowner check
- Power cycle; note brownouts
- Technician scope
- Reactor, IPM, PCB
PC 02
Compressor top / IPM temperature protection
- Homeowner check
- Clear outdoor airflow, power cycle
- Technician scope
- High-pressure protector, IPM, fan
PC 03
Pressure protection (high/low)
- Homeowner check
- NONE - technician
- Technician scope
- Pressure protectors, refrigerant charge
PC 04
Inverter compressor drive error
- Homeowner check
- Power cycle
- Technician scope
- Compressor, IPM, outdoor PCB
PC 06
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 08
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 0A
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 0F
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 10
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 11
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 12
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 30
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 31
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 40
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 43
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 44
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 45
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 46
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 49
Additional outdoor-auxiliary-board diagnostic code captured in source parse
- Homeowner check
- Power cycle once
- Technician scope
- Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3
PC 0L
Low ambient temperature protection
- Homeowner check
- None - below operating temp; wait for warmer temps
- Technician scope
- N/A (operating limit)
PH 90
High temperature protection of the evaporator.
- Homeowner check
- MRCOOL's service manual lists this code without a documented procedure.
- Technician scope
- No MRCOOL service-manual procedure is published for this code; do not infer repairs until a better source exists.
PH 91
Low temperature protection of the evaporator.
- Homeowner check
- MRCOOL's service manual lists this code without a documented procedure.
- Technician scope
- No MRCOOL service-manual procedure is published for this code; do not infer repairs until a better source exists.