MrCool Air Conditioners Error Codes

E0

Indoor unit displays E0 and will not respond to remote commands or only runs in a default mode.

Indoor Unit EEPROM Parameter Error

E1

Indoor unit shows E1 and stops cooling or heating; system may shut down shortly after startup.

High-Pressure Protection / Refrigerant System Overpressure

E2

Indoor unit displays E2 and cooling or heating stops; unit may run briefly then shut down.

Indoor Evaporator Coil Freeze Protection / Low Temperature Protection

E3

Indoor unit shows E3 and system shuts down, often during hot weather or heavy load.

Low-Pressure Protection / Refrigerant System Underpressure

E4

Indoor unit displays E4 and stops; may occur during heating mode on heat pump models.

Compressor Discharge High Temperature Protection

E5

Indoor unit shows E5 and system will not run or shuts down shortly after starting.

Overcurrent Protection / Compressor Overload

E6

Indoor unit displays E6 and does not respond properly; outdoor unit may not start.

Communication Failure Between Indoor and Outdoor Units

E7

Indoor unit shows E7; system may not start or may run erratically.

Mode Conflict or Indoor Unit/Outdoor Unit Mismatch

E8

Indoor unit displays E8 and may shut down; often associated with overheating.

Indoor Fan Motor or Overload Protection Fault

E9

Indoor unit shows E9 and may stop; sometimes associated with defrost or sensor issues.

Water Overflow / Condensate Protection or EEPROM Error (model-dependent)

F0

Indoor unit displays F0 and system will not operate normally.

Refrigerant Undercharge / Low Refrigerant Protection

F1

Indoor unit shows F1 and may run erratically or shut down.

Indoor Ambient Temperature Sensor (T1) Fault

F2

Indoor unit displays F2 and may stop cooling or heating.

Indoor Evaporator Coil Temperature Sensor (T2) Fault

F3

Indoor unit shows F3; system may shut down or defrost improperly in heat mode.

Outdoor Coil Temperature Sensor (T3) Fault

F4

Indoor unit displays F4 and system may not heat or cool correctly.

Outdoor Ambient Temperature Sensor (T4) Fault

F5

Indoor unit shows F5; system may have difficulty controlling temperature or may shut down.

Discharge Pipe Temperature Sensor (T5) Fault

F6

Indoor unit displays F6 and may limit capacity or shut down.

Indoor Fan Speed Out of Control / Feedback Error

F7

Indoor unit shows F7; system may not respond correctly to commands or may shut down.

Outdoor Fan Speed Out of Control / Feedback Error

F8

Indoor unit displays F8 and may limit operation or shut down.

Indoor Unit Overload / Overheating Protection

F9

Indoor unit shows F9; system may not defrost properly or may shut down in heat mode.

Defrost Protection / Outdoor Coil Low Temperature Abnormality

H1

Indoor unit displays H1 and heating is temporarily unavailable.

Defrost Mode Active (Heat Pump)

H3

Indoor unit shows H3 and heating or cooling stops.

Compressor Overload Protection (Thermal Trip)

H5

Indoor unit displays H5 and system will not run.

IPM (Intelligent Power Module) Protection

HC

Indoor unit shows HC and may shut down or limit operation.

Heater or Electric Heat Module Protection (on applicable models)

P0

Indoor unit displays P0 and system may not start or may run at reduced capacity.

Inverter Module Protection / DC Bus Voltage Abnormal

P1

Indoor unit shows P1; system may shut down during operation.

High or Low Voltage Protection

P2

Indoor unit displays P2 and may stop cooling or heating.

Compressor Overload / High Temperature Protection

P3

Indoor unit shows P3; system may limit capacity or shut down intermittently.

Outdoor Low Temperature Protection / Anti-freeze Protection

P4

Indoor unit displays P4 and system may not start or may shut down quickly.

Inverter Compressor Drive Error / IPM Module Protection

Symptom

Air conditioner runs but does not cool the room effectively; supply air feels only slightly cooler than room air.

Insufficient Cooling Capacity / Performance Degradation

Symptom

Indoor unit displays lights or symbols but airflow is weak even on high fan speed.

Restricted Indoor Airflow

Symptom

Indoor unit displays temperature but does not respond to mode or temperature changes; stuck in one mode.

Control Logic or Keypad Lock Malfunction

Symptom

Indoor unit frequently turns on and off (short cycling) without reaching set temperature.

Short Cycling / Control or Sizing Issue

Symptom

Loud humming or grinding noise from the outdoor unit; fan may be slow or not start.

Outdoor Fan or Compressor Mechanical Noise

Symptom

Loud rattling, buzzing, or vibration noise from the indoor unit during operation.

Indoor Mechanical Vibration / Loose Components

Symptom

Outdoor unit fan runs but compressor does not start; no cooling or heating produced.

Compressor Start Failure

Symptom

Outdoor unit runs but indoor fan does not blow air; indoor unit appears powered but no airflow.

Indoor Blower Failure

Symptom

Remote control does not operate the indoor unit; unit only responds to buttons on the front panel (if present).

Remote Control or IR Receiver Failure

Symptom

Strong musty or moldy odor from the indoor unit when it starts or runs.

Biological Growth on Evaporator Coil and Drain Pan

Symptom

Unit blows air but there is a noticeable chemical or refrigerant-like smell.

Possible Refrigerant Leak or Contaminant Odor

Symptom

Unit trips the breaker immediately or shortly after starting.

Electrical Overload or Short Circuit

Symptom

Unit will not power on at all; no lights on indoor display and no response to remote.

No Power to Indoor Unit

Symptom

Water dripping from the front of the indoor unit or down the wall during cooling operation.

Condensate Drainage Failure