Keystone
Keystone 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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CF
Keystone air conditioner displays CF after a certain number of operating hours.
Filter Clean Reminder
E0
Keystone air conditioner shows E0 and may not respond to controls or may be locked.
EEPROM / Memory Error or Control Lock
E1
Keystone window or portable air conditioner displays E1 and stops cooling or controls are unresponsive.
Room Temperature Sensor (Thermistor) Fault
E2
Keystone air conditioner shows E2 and may run briefly then shut off or not start cooling.
Evaporator Coil Temperature Sensor Fault
E3
Keystone air conditioner displays E3 and compressor may not start or shuts down quickly.
Condenser Coil Temperature Sensor Fault
E4
Keystone portable or window air conditioner shows E4 and may stop cooling or enter protection mode.
Defrost / Frost Protection Sensor Error or Overload Protection
E5
Keystone portable air conditioner shows E5 and stops cooling, often related to water tank or drainage.
Full Condensate Tank / Drainage Fault
E6
Keystone air conditioner displays E6 and may not respond to remote or panel commands properly.
Communication Error Between Display Board and Main Control Board
E7
Keystone air conditioner shows E7 and may not operate in certain modes or may shut down unexpectedly.
Mode Control or Fan Motor Feedback Error
E8
Keystone air conditioner displays E8 and may shut down or not start, often related to overheat or overload.
Overload / High Temperature Protection Fault
E9
Keystone portable air conditioner shows E9 and stops operating, often associated with water level or pump issues.
Condensate Pump / Overflow Protection Error
EC
Keystone air conditioner shows EC and stops cooling; may restart briefly then shut down again.
Refrigerant System / Low Refrigerant or Sensor Error
F1
Keystone air conditioner displays F1 and may not respond correctly to temperature settings.
Indoor Ambient Temperature Sensor Calibration / Fault
F2
Keystone air conditioner shows F2 and may cycle erratically or shut down.
Evaporator Coil Sensor Calibration / Fault
F3
Keystone air conditioner displays F3 and may not cool properly or may shut down under load.
Condenser Coil Sensor Calibration / Fault
H1
Keystone air conditioner shows H1 and may run the fan only or pause cooling, often in low ambient conditions.
Defrost / Anti-Frost Protection Active
H2
Keystone air conditioner displays H2 and may limit compressor operation.
High Temperature Protection Active
P1
Keystone portable air conditioner shows P1 and stops cooling.
Bottom Water Reservoir Full / High Water Level
P2
Keystone portable air conditioner displays P2 and may shut down or run fan only.
Upper Water Tray Full / Condensate Management Fault
P3
Keystone portable air conditioner shows P3 and may not start the compressor.
Low Temperature Protection / Freeze Protection
P4
Keystone portable air conditioner displays P4 and may shut down unexpectedly.
Compressor Overload / High Discharge Temperature Protection
Symptom
Keystone air conditioner buttons on the control panel do not respond or respond intermittently.
Keypad / User Interface Failure
Symptom
Keystone air conditioner cycles on and off rapidly (short cycling) without adequately cooling the room.
Short Cycling / Improper Control
Symptom
Keystone air conditioner display and lights work, but the unit does not respond to remote control commands.
Remote Control / IR Receiver Failure
Symptom
Keystone air conditioner does not turn on at all; no lights or display when plugged in.
No Power / Dead Unit
Symptom
Keystone air conditioner emits a burning or electrical smell during operation.
Overheating Electrical Component
Symptom
Keystone air conditioner emits a musty or moldy odor when it starts.
Biological Growth in Evaporator and Drain Pan
Symptom
Keystone air conditioner fan runs continuously even when the compressor cycles off and the set temperature is reached.
Fan Control / Auto Mode Not Working
Symptom
Keystone air conditioner frequently freezes up; ice forms on the evaporator coil and airflow drops.
Evaporator Coil Icing
Symptom
Keystone air conditioner in dehumidify (DRY) mode does not seem to remove much moisture from the air.
Poor Dehumidification Performance
Symptom
Keystone air conditioner leaks water inside the room from the front panel or bottom.
Indoor Water Leakage
Symptom
Keystone air conditioner louvers do not swing or adjust direction automatically.
Air Louver Motor / Linkage Failure
Symptom
Keystone air conditioner makes loud rattling or buzzing noises during operation.
Mechanical Vibration / Loose Components
Symptom
Keystone air conditioner powers on but compressor does not start; fan runs and air is not cold.
Compressor Not Starting
Symptom
Keystone air conditioner produces a high-pitched squealing or screeching noise when the fan runs.
Fan Motor Bearing Wear
Symptom
Keystone air conditioner runs but does not cool the room effectively; air from the front is only slightly cool or room temperature.
Insufficient Cooling / Low Capacity Operation
Symptom
Keystone air conditioner trips the household circuit breaker or blows fuses when starting or during operation.
Overcurrent / Electrical Short
Symptom
Keystone air conditioner turns on but the indoor fan does not blow air; compressor may run and coil may freeze.
Indoor Blower Fan Failure
Symptom
Keystone portable air conditioner leaks water onto the floor around the base.
External Water Leakage from Portable Unit
| Error Code | Symptom | Fault Type | Guide |
|---|---|---|---|
| CF |
Keystone air conditioner displays CF after a certain number of operating hours.
|
Filter Clean Reminder | View Details |
| E0 |
Keystone air conditioner shows E0 and may not respond to controls or may be locked.
|
EEPROM / Memory Error or Control Lock | View Details |
| E1 |
Keystone window or portable air conditioner displays E1 and stops cooling or controls are unresponsive.
|
Room Temperature Sensor (Thermistor) Fault | View Details |
| E2 |
Keystone air conditioner shows E2 and may run briefly then shut off or not start cooling.
|
Evaporator Coil Temperature Sensor Fault | View Details |
| E3 |
Keystone air conditioner displays E3 and compressor may not start or shuts down quickly.
|
Condenser Coil Temperature Sensor Fault | View Details |
| E4 |
Keystone portable or window air conditioner shows E4 and may stop cooling or enter protection mode.
|
Defrost / Frost Protection Sensor Error or Overload Protection | View Details |
| E5 |
Keystone portable air conditioner shows E5 and stops cooling, often related to water tank or drainage.
|
Full Condensate Tank / Drainage Fault | View Details |
| E6 |
Keystone air conditioner displays E6 and may not respond to remote or panel commands properly.
|
Communication Error Between Display Board and Main Control Board | View Details |
| E7 |
Keystone air conditioner shows E7 and may not operate in certain modes or may shut down unexpectedly.
|
Mode Control or Fan Motor Feedback Error | View Details |
| E8 |
Keystone air conditioner displays E8 and may shut down or not start, often related to overheat or overload.
|
Overload / High Temperature Protection Fault | View Details |
| E9 |
Keystone portable air conditioner shows E9 and stops operating, often associated with water level or pump issues.
|
Condensate Pump / Overflow Protection Error | View Details |
| EC |
Keystone air conditioner shows EC and stops cooling; may restart briefly then shut down again.
|
Refrigerant System / Low Refrigerant or Sensor Error | View Details |
| F1 |
Keystone air conditioner displays F1 and may not respond correctly to temperature settings.
|
Indoor Ambient Temperature Sensor Calibration / Fault | View Details |
| F2 |
Keystone air conditioner shows F2 and may cycle erratically or shut down.
|
Evaporator Coil Sensor Calibration / Fault | View Details |
| F3 |
Keystone air conditioner displays F3 and may not cool properly or may shut down under load.
|
Condenser Coil Sensor Calibration / Fault | View Details |
| H1 |
Keystone air conditioner shows H1 and may run the fan only or pause cooling, often in low ambient conditions.
|
Defrost / Anti-Frost Protection Active | View Details |
| H2 |
Keystone air conditioner displays H2 and may limit compressor operation.
|
High Temperature Protection Active | View Details |
| P1 |
Keystone portable air conditioner shows P1 and stops cooling.
|
Bottom Water Reservoir Full / High Water Level | View Details |
| P2 |
Keystone portable air conditioner displays P2 and may shut down or run fan only.
|
Upper Water Tray Full / Condensate Management Fault | View Details |
| P3 |
Keystone portable air conditioner shows P3 and may not start the compressor.
|
Low Temperature Protection / Freeze Protection | View Details |
| P4 |
Keystone portable air conditioner displays P4 and may shut down unexpectedly.
|
Compressor Overload / High Discharge Temperature Protection | View Details |
| – |
Keystone air conditioner buttons on the control panel do not respond or respond intermittently.
|
Keypad / User Interface Failure | View Details |
| – |
Keystone air conditioner cycles on and off rapidly (short cycling) without adequately cooling the room.
|
Short Cycling / Improper Control | View Details |
| – |
Keystone air conditioner display and lights work, but the unit does not respond to remote control commands.
|
Remote Control / IR Receiver Failure | View Details |
| – |
Keystone air conditioner does not turn on at all; no lights or display when plugged in.
|
No Power / Dead Unit | View Details |
| – |
Keystone air conditioner emits a burning or electrical smell during operation.
|
Overheating Electrical Component | View Details |
| – |
Keystone air conditioner emits a musty or moldy odor when it starts.
|
Biological Growth in Evaporator and Drain Pan | View Details |
| – |
Keystone air conditioner fan runs continuously even when the compressor cycles off and the set temperature is reached.
|
Fan Control / Auto Mode Not Working | View Details |
| – |
Keystone air conditioner frequently freezes up; ice forms on the evaporator coil and airflow drops.
|
Evaporator Coil Icing | View Details |
| – |
Keystone air conditioner in dehumidify (DRY) mode does not seem to remove much moisture from the air.
|
Poor Dehumidification Performance | View Details |
| – |
Keystone air conditioner leaks water inside the room from the front panel or bottom.
|
Indoor Water Leakage | View Details |
| – |
Keystone air conditioner louvers do not swing or adjust direction automatically.
|
Air Louver Motor / Linkage Failure | View Details |
| – |
Keystone air conditioner makes loud rattling or buzzing noises during operation.
|
Mechanical Vibration / Loose Components | View Details |
| – |
Keystone air conditioner powers on but compressor does not start; fan runs and air is not cold.
|
Compressor Not Starting | View Details |
| – |
Keystone air conditioner produces a high-pitched squealing or screeching noise when the fan runs.
|
Fan Motor Bearing Wear | View Details |
| – |
Keystone air conditioner runs but does not cool the room effectively; air from the front is only slightly cool or room temperature.
|
Insufficient Cooling / Low Capacity Operation | View Details |
| – |
Keystone air conditioner trips the household circuit breaker or blows fuses when starting or during operation.
|
Overcurrent / Electrical Short | View Details |
| – |
Keystone air conditioner turns on but the indoor fan does not blow air; compressor may run and coil may freeze.
|
Indoor Blower Fan Failure | View Details |
| – |
Keystone portable air conditioner leaks water onto the floor around the base.
|
External Water Leakage from Portable Unit | View Details |
No matching codes found
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