Day & Night
Day & Night Air Conditioners Error Codes
Complete list of fault codes and troubleshooting guides. Use the search below to find your specific error.
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E0
Indoor unit display shows E0 and system will not start cooling or heating
Indoor Unit EEPROM/PCB Communication Fault
E1
E1 displayed on indoor unit, outdoor unit does not start, no cooling
Indoor–Outdoor Communication Failure
E2
E2 on indoor display, unit runs briefly then shuts down, poor temperature control
Indoor Coil Temperature Sensor (Thermistor) Fault
E3
E3 error, outdoor fan may stop, unit shuts down on hot days
Outdoor Coil Temperature Sensor Fault
E4
E4 displayed, compressor stops, unit may run fan only
High-Pressure Protection / Discharge Overheat
E5
E5 error, compressor does not start or trips quickly, outdoor fan may run
Compressor Overcurrent / Overload Protection
E6
E6 on display, indoor fan may run but no cooling, intermittent operation
Outdoor Unit EEPROM/PCB Fault
E7
E7 error, unit may start and stop frequently, poor cooling performance
Mode Conflict / Indoor Fan or Reversing Valve Control Error (Heat Pump Models)
E8
E8 displayed, unit shuts down after running, may restart after a while
Indoor Fan Motor Overload / Overheat Protection
E9
E9 error, unit may not respond to thermostat commands or may run unexpectedly
Indoor Unit EEPROM Configuration / Addressing Error
F0
F0 code on display, unit stops cooling, may restart after long delay
Refrigerant System Low Charge / Low Pressure Protection
F1
F1 code, unit may run at reduced capacity or shut down intermittently
High Discharge Temperature / Compressor Overheat
F2
F2 error, indoor unit may blow room-temperature air, system cycles frequently
Room Temperature Sensor (Thermistor) Fault
F3
F3 code, unit may not defrost properly in heat pump mode, frost buildup on outdoor coil
Defrost Sensor / Defrost Control Fault (Heat Pump)
F4
F4 error, outdoor fan may not run or runs erratically, unit overheats
Outdoor Fan Motor or Fan Feedback Fault
F5
F5 code, unit may short-cycle or fail to maintain setpoint
Indoor–Outdoor Capacity Mismatch / Configuration Error
H0
H0 code, unit does not start, display may be blank or show only H0
Low Voltage / Power Supply Fault
H1
H1 code, heat pump may run in backup heat only, poor heating performance
Outdoor Temperature Sensor Fault (Heat Pump)
H2
H2 code, auxiliary heat may run excessively, high electric bills
Defrost Termination / Outdoor Coil Sensor Error (Heat Pump)
H3
H3 code, compressor locked out, unit may run fan only
Compressor Overload / Thermal Protection Lockout
H4
H4 code, unit does not respond to thermostat, both indoor and outdoor may be idle
Communication Loss Between Thermostat and Indoor Unit (Communicating Systems)
H5
H5 code, unit may run at limited capacity or lock out after several attempts
Inverter Module Protection (Inverter-Driven Models)
Symptom
Breaker for outdoor unit trips repeatedly when AC starts
Electrical Overload / Short Circuit
Symptom
Burning or electrical smell from indoor or outdoor unit
Overheating Electrical Component
Symptom
Clicking from indoor unit but blower does not start; sometimes starts after several tries
ECM Blower Motor Control Failure
Symptom
Heat pump blows cool air in heating mode; outdoor unit may be iced over
Defrost Cycle Failure (Heat Pump)
Symptom
High-pitched squealing or screeching noise from indoor unit
Blower Motor or Wheel Bearing Failure
Symptom
Indoor coil freezes into a block of ice; little or no airflow from vents
Evaporator Coil Freeze-Up
Symptom
Indoor unit blows warm air in cooling mode; outdoor unit not running
Thermostat or Control Signal Failure
Symptom
Indoor unit does not start at all; no blower, no display, thermostat blank
No Power to Indoor Unit
Symptom
Loud banging or rattling noise from outdoor unit during operation
Mechanical Vibration / Fan or Mounting Issue
Symptom
Musty or moldy odor from supply vents when AC runs
Biological Growth in Evaporator Coil or Drain Pan
Symptom
Outdoor fan runs but compressor does not; loud humming from outdoor unit
Failed Compressor Start Circuit / Run Capacitor
Symptom
Outdoor unit runs but indoor blower does not start; weak or no airflow from registers
Indoor Blower Motor Failure
Symptom
Outdoor unit runs continuously and cannot reach set temperature on hot days
Capacity Loss / System Undersizing or Performance Degradation
Symptom
Outdoor unit vibrates excessively and is very noisy at startup
Compressor Mounting or Internal Mechanical Issue
Symptom
Outdoor unit will not start at all; indoor blower runs and thermostat calls for cooling
Outdoor Contactor or Control Circuit Failure
Symptom
System runs but does not cool well; supply air only slightly cooler than room air
Low Refrigerant Charge / Minor Leak
Symptom
System short cycles (turns on and off frequently) and does not maintain temperature
Improper Thermostat Location or Oversized Equipment
Symptom
Uneven cooling in different rooms; some rooms too hot, others too cold
Ductwork Imbalance / Air Distribution Issue
Symptom
Water leaking from indoor unit or around air handler; water on floor near furnace
Condensate Drain Blockage / Pan Overflow
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| E0 |
Indoor unit display shows E0 and system will not start cooling or heating
|
Indoor Unit EEPROM/PCB Communication Fault | View Details |
| E1 |
E1 displayed on indoor unit, outdoor unit does not start, no cooling
|
Indoor–Outdoor Communication Failure | View Details |
| E2 |
E2 on indoor display, unit runs briefly then shuts down, poor temperature control
|
Indoor Coil Temperature Sensor (Thermistor) Fault | View Details |
| E3 |
E3 error, outdoor fan may stop, unit shuts down on hot days
|
Outdoor Coil Temperature Sensor Fault | View Details |
| E4 |
E4 displayed, compressor stops, unit may run fan only
|
High-Pressure Protection / Discharge Overheat | View Details |
| E5 |
E5 error, compressor does not start or trips quickly, outdoor fan may run
|
Compressor Overcurrent / Overload Protection | View Details |
| E6 |
E6 on display, indoor fan may run but no cooling, intermittent operation
|
Outdoor Unit EEPROM/PCB Fault | View Details |
| E7 |
E7 error, unit may start and stop frequently, poor cooling performance
|
Mode Conflict / Indoor Fan or Reversing Valve Control Error (Heat Pump Models) | View Details |
| E8 |
E8 displayed, unit shuts down after running, may restart after a while
|
Indoor Fan Motor Overload / Overheat Protection | View Details |
| E9 |
E9 error, unit may not respond to thermostat commands or may run unexpectedly
|
Indoor Unit EEPROM Configuration / Addressing Error | View Details |
| F0 |
F0 code on display, unit stops cooling, may restart after long delay
|
Refrigerant System Low Charge / Low Pressure Protection | View Details |
| F1 |
F1 code, unit may run at reduced capacity or shut down intermittently
|
High Discharge Temperature / Compressor Overheat | View Details |
| F2 |
F2 error, indoor unit may blow room-temperature air, system cycles frequently
|
Room Temperature Sensor (Thermistor) Fault | View Details |
| F3 |
F3 code, unit may not defrost properly in heat pump mode, frost buildup on outdoor coil
|
Defrost Sensor / Defrost Control Fault (Heat Pump) | View Details |
| F4 |
F4 error, outdoor fan may not run or runs erratically, unit overheats
|
Outdoor Fan Motor or Fan Feedback Fault | View Details |
| F5 |
F5 code, unit may short-cycle or fail to maintain setpoint
|
Indoor–Outdoor Capacity Mismatch / Configuration Error | View Details |
| H0 |
H0 code, unit does not start, display may be blank or show only H0
|
Low Voltage / Power Supply Fault | View Details |
| H1 |
H1 code, heat pump may run in backup heat only, poor heating performance
|
Outdoor Temperature Sensor Fault (Heat Pump) | View Details |
| H2 |
H2 code, auxiliary heat may run excessively, high electric bills
|
Defrost Termination / Outdoor Coil Sensor Error (Heat Pump) | View Details |
| H3 |
H3 code, compressor locked out, unit may run fan only
|
Compressor Overload / Thermal Protection Lockout | View Details |
| H4 |
H4 code, unit does not respond to thermostat, both indoor and outdoor may be idle
|
Communication Loss Between Thermostat and Indoor Unit (Communicating Systems) | View Details |
| H5 |
H5 code, unit may run at limited capacity or lock out after several attempts
|
Inverter Module Protection (Inverter-Driven Models) | View Details |
| – |
Breaker for outdoor unit trips repeatedly when AC starts
|
Electrical Overload / Short Circuit | View Details |
| – |
Burning or electrical smell from indoor or outdoor unit
|
Overheating Electrical Component | View Details |
| – |
Clicking from indoor unit but blower does not start; sometimes starts after several tries
|
ECM Blower Motor Control Failure | View Details |
| – |
Heat pump blows cool air in heating mode; outdoor unit may be iced over
|
Defrost Cycle Failure (Heat Pump) | View Details |
| – |
High-pitched squealing or screeching noise from indoor unit
|
Blower Motor or Wheel Bearing Failure | View Details |
| – |
Indoor coil freezes into a block of ice; little or no airflow from vents
|
Evaporator Coil Freeze-Up | View Details |
| – |
Indoor unit blows warm air in cooling mode; outdoor unit not running
|
Thermostat or Control Signal Failure | View Details |
| – |
Indoor unit does not start at all; no blower, no display, thermostat blank
|
No Power to Indoor Unit | View Details |
| – |
Loud banging or rattling noise from outdoor unit during operation
|
Mechanical Vibration / Fan or Mounting Issue | View Details |
| – |
Musty or moldy odor from supply vents when AC runs
|
Biological Growth in Evaporator Coil or Drain Pan | View Details |
| – |
Outdoor fan runs but compressor does not; loud humming from outdoor unit
|
Failed Compressor Start Circuit / Run Capacitor | View Details |
| – |
Outdoor unit runs but indoor blower does not start; weak or no airflow from registers
|
Indoor Blower Motor Failure | View Details |
| – |
Outdoor unit runs continuously and cannot reach set temperature on hot days
|
Capacity Loss / System Undersizing or Performance Degradation | View Details |
| – |
Outdoor unit vibrates excessively and is very noisy at startup
|
Compressor Mounting or Internal Mechanical Issue | View Details |
| – |
Outdoor unit will not start at all; indoor blower runs and thermostat calls for cooling
|
Outdoor Contactor or Control Circuit Failure | View Details |
| – |
System runs but does not cool well; supply air only slightly cooler than room air
|
Low Refrigerant Charge / Minor Leak | View Details |
| – |
System short cycles (turns on and off frequently) and does not maintain temperature
|
Improper Thermostat Location or Oversized Equipment | View Details |
| – |
Uneven cooling in different rooms; some rooms too hot, others too cold
|
Ductwork Imbalance / Air Distribution Issue | View Details |
| – |
Water leaking from indoor unit or around air handler; water on floor near furnace
|
Condensate Drain Blockage / Pan Overflow | View Details |
No matching codes found
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