HVAC Toolkit
L

Lennox Error Codes

Inverter Mini-Splits & Air Conditioners ยท USA

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

E-Series (System/Sensor Errors)

Code Description Possible Cause Action
E1 High pressure protection Discharge pressure too high, condenser blockage or overcharge Check condenser coil, clean if dirty, verify refrigerant charge and outdoor fan operation
E2 Anti-freezing protection Evaporator coil temperature too low, low airflow or low charge Check air filter, indoor fan, refrigerant charge, and expansion valve
E3 Low pressure protection Suction pressure too low, refrigerant leak or restriction Check for leaks, verify charge, inspect filter drier and expansion valve
E4 High discharge temperature protection Compressor discharge temperature excessive Check refrigerant charge, condenser airflow, and compressor valves
E5 Whole unit overcurrent protection System drawing excess current Check power supply voltage, compressor windings, and wiring connections
E6 Indoor/outdoor communication error Communication wire fault between indoor and outdoor units Check communication wiring, connectors, and PCB boards on both units
E7 Running mode conflict Multiple indoor units requesting conflicting modes (heat vs cool) Set all indoor units to same mode, check mode settings via remote
E8 Overload protection Compressor overload due to high pressure or mechanical issue Check condenser, refrigerant charge, compressor, and ambient conditions
E9 Indoor unit full water error Condensate drain pan full, float switch triggered Clean drain line, check drain pump, clear blockage in condensate piping
EU IPM temperature protection / frequency limited Inverter power module overheating Check outdoor unit airflow, clean heat sink, verify fan operation

F-Series (Sensor/Protection Codes)

Code Description Possible Cause Action
F0 System charge shortage or blockage Low refrigerant or restriction in refrigerant circuit Check for leaks, recharge system, inspect filter drier and capillary tube
F1 Return air temperature sensor fault Room temperature thermistor open or short circuit Check sensor wiring, measure resistance, replace thermistor if out of spec
F2 Evaporator temperature sensor fault Indoor coil thermistor open or short circuit Check sensor connection, measure resistance, replace if faulty
F3 Outdoor ambient temperature sensor fault Outdoor ambient thermistor open or short circuit Inspect sensor wiring at outdoor unit, replace thermistor
F4 Condenser coil temperature sensor fault Outdoor coil mid-tube thermistor open or short circuit Check sensor attached to condenser coil, replace if needed
F5 Discharge temperature sensor fault Compressor discharge thermistor open or short circuit Inspect sensor on discharge line, replace if faulty

H-Series (Status/Protection)

Code Description Possible Cause Action
H1 Defrosting in progress Normal defrost cycle active in heat mode No action needed, unit will resume heating after defrost completes
H3 Compressor overheating protection Compressor body temperature too high Check refrigerant charge, airflow, and compressor for mechanical failure
H5 IPM current protection Inverter power module overcurrent detected Check compressor windings, wiring, and inverter board
H6 Compressor motor stalling Compressor rotor locked or unable to start Check compressor, starting circuit, refrigerant pressures, and power supply
H7 Compressor desynchronizing Inverter compressor lost synchronization Check compressor winding resistance, inverter board, and power supply voltage
HC PFC protection Power factor correction circuit fault Check PFC module on outdoor PCB, input voltage, and capacitors

P-Series (Protection Codes)

Code Description Possible Cause Action
P1 High pressure switch open High pressure switch tripped due to excessive pressure Check condenser, outdoor fan, refrigerant charge, reset switch after cooling
P2 Low pressure switch open Low pressure switch tripped due to low suction pressure Check for refrigerant leaks, verify charge, inspect expansion valve
P3 Compressor current overload Outdoor compressor drawing excessive current Check compressor windings, voltage, and mechanical condition
P4 High compressor discharge temperature Discharge line temperature exceeds limit Check superheat, refrigerant charge, compressor valves
P5 Over phase current protection Phase current exceeds safe limit Check power supply, compressor, and inverter board
PH DC bus over-voltage protection DC bus voltage too high in inverter circuit Check input voltage, rectifier, and DC bus capacitors
PL DC bus under-voltage protection DC bus voltage too low in inverter circuit Check input voltage, power supply wiring, and rectifier circuit

L-Series (Inverter Codes)

Code Description Possible Cause Action
LC Compressor startup failure Compressor failed to start within time limit Check compressor windings, power supply, refrigerant pressures
LD Compressor phase loss/reversal Phase sequence incorrect or phase missing (3-phase units) Check 3-phase wiring, swap two phases if reversed
L3 Outdoor fan motor error Outdoor fan motor 1 failure or speed abnormal Check fan motor, wiring, capacitor, and fan blade for obstruction

Lennox 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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