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Heat Pump Error Codes & Troubleshooting

Look up error codes from top heat pump brands. Understand what they mean and when to call an emergency technician.

U2HIGH

Serial Communication Error (Mitsubishi)

Mitsubishi heat pump serial communication between indoor and outdoor units has been lost.

Mitsubishi
E6HIGH

Indoor/Outdoor Communication Error (Mitsubishi)

Mitsubishi heat pump indoor unit and outdoor unit have lost communication between each other.

Mitsubishi
P1MEDIUM

Intake Air Temperature Sensor Error (Mitsubishi)

Mitsubishi heat pump indoor intake air temperature sensor is reading outside valid range.

Mitsubishi
A1HIGH

PCB Fault (Daikin)

Daikin heat pump printed circuit board has detected an internal fault.

Daikin
A5MEDIUM

Freeze Prevention Active (Daikin)

Daikin heat pump has activated freeze prevention mode, temporarily stopping operation.

Daikin
H0HIGH

Compressor Sensor Error (Daikin)

Daikin heat pump compressor temperature or pressure sensor has failed.

Daikin
01MEDIUM

Thermistor Error (Fujitsu)

Fujitsu heat pump temperature thermistor is reading outside the valid operating range.

Fujitsu
02CRITICAL

Compressor Startup Error (Fujitsu)

Fujitsu heat pump compressor failed to start properly within the expected time frame.

Fujitsu
03HIGH

Communication Error (Fujitsu)

Fujitsu heat pump communication error between indoor and outdoor control assemblies.

Fujitsu
CH05HIGH

Outdoor Unit PCB Error (LG)

LG heat pump outdoor unit control PCB has detected a fault and cannot operate.

LG
CH44HIGH

DC Link Voltage Error (LG)

LG heat pump inverter DC link voltage is outside the acceptable operating range.

LG
65HIGH

Indoor Fan Motor Fault (Samsung)

Samsung heat pump indoor fan motor is not operating at the correct speed or has stalled.

Samsung
66HIGH

Outdoor Fan Motor Fault (Samsung)

Samsung heat pump outdoor fan motor has failed or is not operating correctly.

Samsung
E0MEDIUM

Outdoor Unit EEPROM Error (Carrier)

Carrier heat pump outdoor control board EEPROM data is corrupted or unreadable.

Carrier
89CRITICAL

Inverter Module Error (Trane)

Trane heat pump inverter drive module has detected a fault and cannot operate the compressor.

Trane
E3CRITICAL

High Pressure Switch Trip (Carrier)

Carrier heat pump high pressure switch has opened due to excessive refrigerant pressure.

CarrierTrane
E4HIGH

Low Pressure Switch Trip (Trane)

Trane heat pump low pressure switch has opened due to suction pressure dropping too low.

TraneCarrier
8MEDIUM

Defrost Sensor Error (Mitsubishi)

Mitsubishi heat pump defrost temperature sensor has failed open or short circuit.

Mitsubishi
H9MEDIUM

Outdoor Air Thermistor Error (Daikin)

Daikin heat pump outdoor air temperature sensor has failed.

Daikin
E5CRITICAL

Compressor Overload Protection (LG)

LG heat pump compressor overload protection has activated due to excessive current draw.

LG
F6HIGH

Outdoor Unit Refrigerant Leak Detection (Fujitsu)

Fujitsu heat pump refrigerant leak detection sensor has activated.

Fujitsu
E251HIGH

Communication Error Between Units (Samsung)

Samsung heat pump communication loss between indoor and outdoor units.

Samsung
E7HIGH

Outdoor Unit Fan Motor Locked (Carrier)

Carrier heat pump outdoor fan motor is locked or drawing excessive current.

Carrier

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