HVAC Toolkit
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Bosch Error Codes

Inverter Mini-Splits & Air Conditioners ยท Germany

Prefixes: E=System/Sensor, F=Sensor/Protection, P=Protection, H=Status

E-Series (System/Sensor Errors)

Code Description Possible Cause Action
E0 Indoor unit EEPROM parameter error Indoor PCB EEPROM data corrupted or missing Power cycle the unit, replace indoor PCB if error persists
E1 Indoor/outdoor communication error Communication wire fault between indoor and outdoor units Check communication wiring, polarity, connectors, and both PCBs
E2 Zero-crossing signal detection error AC power zero-crossing circuit failure on indoor PCB Check power supply, replace indoor PCB if error continues
E3 Indoor fan speed out of control Indoor fan motor not running at correct speed Check fan motor, wiring, capacitor, and indoor PCB fan driver
E4 Room temperature sensor T1 fault Indoor room thermistor open or short circuit Check sensor wiring, measure resistance, replace thermistor if faulty
E5 Evaporator coil temperature sensor T2 fault Indoor coil thermistor open or short circuit Inspect sensor on evaporator coil, replace if resistance out of spec
E6 Indoor/outdoor unit communication fault Serial communication failure between units Check communication cable, verify correct wiring, inspect PCB connectors
EC Refrigerant leakage detection Built-in refrigerant leak sensor triggered Perform leak test with electronic detector, repair leak, recharge system
E7 Outdoor DC fan motor fault DC fan motor failure or speed signal lost Check fan motor wiring, hall sensor, replace motor if faulty
E8 Compressor discharge sensor unseated T5 sensor not properly attached to discharge line Reattach discharge sensor securely to pipe, use thermal paste and insulation
E9 Outdoor EEPROM fault Outdoor unit EEPROM chip failure Replace outdoor control board

F-Series (Sensor/Protection Codes)

Code Description Possible Cause Action
F0 Overload current protection System drawing excessive current beyond rated limit Check compressor, power supply voltage, and wiring connections
F1 Outdoor ambient temperature sensor T4 fault Outdoor ambient thermistor open or short circuit Check sensor wiring on outdoor unit, replace thermistor if needed
F2 Condenser coil temperature sensor T3 fault Condenser coil thermistor open or short circuit Inspect sensor on condenser coil, check connector, replace if faulty
F3 Discharge temperature sensor T5 fault Compressor discharge thermistor open or short circuit Check sensor on discharge line, replace if resistance out of range
F4 Outdoor unit EEPROM parameter error Outdoor PCB EEPROM data corrupted or missing Power cycle outdoor unit, replace outdoor PCB if error persists
F5 Outdoor fan speed out of control Outdoor fan motor not running at expected speed Check fan motor, blade obstruction, wiring, and outdoor PCB
F6 T2b sensor error Indoor coil outlet pipe temperature sensor fault Check T2b sensor wiring and connector, replace if faulty

P-Series (Protection Codes)

Code Description Possible Cause Action
P0 Inverter module (IPM) malfunction IPM overcurrent or overtemperature protection Check compressor windings, inverter board, heat sink, and wiring
P1 Over-voltage or under-voltage protection Input voltage or DC bus voltage out of range Check incoming voltage with multimeter, inspect rectifier and capacitors
P2 Compressor top high temperature protection Compressor shell temperature exceeds safe limit (OLP) Check refrigerant charge, superheat, condenser airflow, compressor valves
P3 Low ambient temperature cut-off Outdoor temperature below minimum operating threshold Unit cannot operate in extreme cold; check ambient sensor for accuracy
P4 High compressor discharge temperature protection Discharge line temperature exceeds safe limit Check superheat, refrigerant charge, and condenser coil cleanliness
P5 Condenser coil temperature protection in cooling Condenser coil temperature too high during cooling mode Clean condenser coil, check outdoor fan motor, verify charge
P6 Evaporator overheating protection in cooling Evaporator coil temperature too high in cooling mode Check indoor airflow, filter, fan motor, and refrigerant charge
P7 Overheating protection in heating mode Condenser (indoor coil in heating) temperature too high Check indoor airflow, air filter, and fan motor operation
P8 DC fan motor hurricane protection Outdoor DC fan motor reverse rotation detected from strong wind Check fan motor and blade, verify no extreme wind condition

Other Codes

Code Description Possible Cause Action
CF Anti-cold wind mode Normal startup delay to prevent cold air in heating mode No action needed, system will begin heating once coil warms up
dF Defrost mode active Normal defrost cycle running in heating mode No action needed, unit will resume heating after defrost completes

Bosch Troubleshooting Tips

Before Calling for Service

  • Turn off unit, wait 5 minutes, then restart - some errors auto-reset
  • Check and clean air filters - many errors caused by restricted airflow
  • Verify power supply voltage is within specification
  • Check circuit breaker and disconnect switch
  • Note the exact error code and when it occurs for technician

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