McQuay air conditioner error codes

Reading split systems’ error codes can help users trace the cause of a fault and eliminate it. Almost all ACs feature a self-diagnosis function, which enables the device to analyze its operability (circuitry, units) and shows detected faults as error codes on the remote control or the device’s display screen. Codes appear as combinations of digits or flashing light, diode, etc.

McQuay GS01 air conditioner error codes

A1Indoor pcb error
A3Drain pump abnormal
A5Antifreeze (cooling)/heat exchanger overheat (heating)
A6Indoor fan motor abnormal
AHElectrical air cleaner abnormal
C4Indoor heat exchanger (1) thermistor short/open
C5Indoor heat exchanger (2) thermistor short/open
ClLouver limit switch error
C9Indoor room thermistor short/open
ElOutdoor pcb error
E3High pressure protection
E4Low pressure protection
E5Compressor motor lock/compressor overloaded
E6Compressor start-up error
E7Outdoor dc fan motor lock
E8Ac input over current
E9Exv error
EA4 way valve error
F3Discharge pipe overheat
F6Heat exchanger overheat
HOCompressor sensor system error
H3High pressure switch error
H6Compressor feedback detection error
H7Fan motor overloaded/overcurrent/sensor abnormal
H8Ac current sensor error
H9Outdoor air thermistor short/open
J1Pressure sensor error
J3Compressor discharge pipe thermistor short/open/misplaced
J5Suction pipe thermistor short/open
J6Outdoor heat exchanger thermistor short/open
J7Subcooling heat exchanger thermistor short/open
J8Liquid pipe thermistor short/open
J9Gas pipe thermistor short/open
LIInverter outdoor pcb error
L3Outdoor control box overheat
L4Heat sink overheat
L5Ipm error/igbt error
L8Inverter compressor overcurrent
L9Compressor overcurrent prevention
LCCommunication error (outdoor control pcb and inverter pcb)
PIOpen phase or voltage unbalance
P4Heat sink thermistor short/open
PJCapacity setting error
UOInsufficient gas
U2Dc voltage out of range
U4Communication error
U7Communication error (outdoor control pcb and ipm pcb)
UAInstallation error
UFPiping & wiring installation mismatch/wrong wiring/insufficient gas
UHAntifreeze (other rooms)

McQuay MCK020A air conditioner error codes

Error Code at 7 segment DisplayOperation/ Faulty Indication
E1 BlinkingRoom sensor contact loose/ short
E2 BlinkingIndoor coil sensor contact loose/ short
E3 BlinkingOutdoor coil sensor contact loose/ short
E4 BlinkingCompressor overload
E5 BlinkingGas leak
E6 BlinkingPump faulty
Heat LED BlinkingOutdoor defrost (for Heatpump only)

McQuay McQuay MWM air conditioner error codes

1E0System malfunction
2E1Sensor Broken (TH1 discharge Temp.)
3E2Sensor Broken (TH2 inlet coil 1#)
4E3Sensor Broken (TH3 mid coil 1#)
5E4Sensor Broken (TH4 inlet coil 2#)
6E5Sensor Broken (TH5 mid coil 2#)
7E6Sensor Broken (TH6 inlet coil 3#)
8E7Sensor Broken (TH7 mid coil 3#)
9E8Sensor Broken (TH8 ambient temp)
10E9Sensor Broken (TH9 outlet coil)
11EASensor Broken (TH10 subcool outlet)
12EBSensor Broken (TH11 subcool suction)
13ECSensor Broken (TH12 suction)
14EFEmergency Run
15F0Outdoor Storage Malfunction
16F1Sensor Broken (indoor inlet coil)
17F2Sensor Broken (indoor mid coil)
18F3Sensor Broken (indoor outlet coil)
19F4Sensor Broken (indoor return air)
20F5Sensor Broken (indoor supply air)
21F6Indoor and controller communication malfunction
22F7Ambient temp exceed the limit
23re4WV malfunction
24F9Refrigerant leakage
25FAController storage malfunction
26FBWater Pump (indoor water pump)
27FCIndoor and outdoor communication malfunction
28FEMaster and slave communication malfunction
29HODigital comp overload
30H1Fixed Compl overload
31H2Fixed Comp2 overload
32H3Fixed Comp3 overload
33H4High pressure too high
34H5Sensor broken, high pressure
35H6Discharge temp too high
36L0Super heat too low
37L1Low pressure too low
38L2Sensor broken, low pressure
3910System malfunction
4011Sensor broken (slave TH1 discharge temp)
4112Sensor broken (slave TH2 inlet coil 1#)
4213Sensor Broken (slave TH3 mid coil 1#)
4314Sensor broken (slave TH4 inlet coil 2#)
4415Sensor broken (slave TH5 mid coil 2#)
4516Sensor broken (slave TH6 inlet coil 3#)
4617Sensor broken (slave TH7 mid coil 3#)
4718Sensor broken (slave TH8 ambient temp)
4819Sensor broken (slave TH9 outlet coil)
491ASensor broken (slave TH10 subcool outlet)
501BSensor broken (slave TH11 subcool suction)
511CSensor Broken (slave TH12 suction)
521FEmergency run (slave)
5320Outdoor storage (slave)
5427Ambient temp exceed the limit (slave)
55284WV malfunction (slave)
5629Refrigerant leakage (slave)
5730Digital comp overload (slave)
5831Fixed compl overload (slave)
5932Fixed comp2 overload
6033Fixed comp 3 overload

McQuay Netware 3C-SLM 9 – Inverter Y Models air conditioner error codes

Error CodeFaulty IndicationError CodeFaulty Indication
0NormalH9Outdoor air thermistor short/open
A1Indoor PCB errorJ1Pressure sensor error
A3Drain pump faultJ3Compressor discharge pipe thermistor short/open/misplaced
A5Antifreeze(Cooling) / Heat exchanger overheat(Heating)J5Suction pipe thermistor short/open
A6Indoor fan motor faultJ6Outdoor heat exchanger thermistor short/open
AHElectrical air cleaner faultJ7Sub cooling heat exchanger thermistor short/open
C4Indoor heat exchanger (1) thermistor short/openJ8Liquid pipe thermistor short/open
C5Indoor heat exchanger (2) thermistor short/openJ9Gas pipe thermistor short/open
C7Louver limit switch errorL1Inverter outdoor PCB error
C9Indoor room thermistor short/openL3Outdoor control box overheat
E1Outdoor PCB errorL4Heat sink overheat
E3High pressure protectionL5IPM error/IGBT error
E4Low pressure protectionL8Electrical thermal switch
E5Compressor motor lock/compressor overloadedL9Stall prevention
E6Compressor start-up errorLCCommunication error (outdoor PCB & inverter PCB)
E7Outdoor DC fan motor lockP1Open phase or voltage unbalance
E8Ac input over currentP4Heat sink thermistor short/open
E9EXV errorPJCapacity setting error
EA4 way valve errorUOInsufficient gas
F3Discharge pipe overheatU2DC voltage out of range
F6Heat exchanger overheatU4Communication error
HOCompressor sensor system errorU7Communication error (outdoor PCB & IPM PCB)
H3High pressure switch errorUAInstallation error
H6Compressor feedback detection errorUFPiping & wiring installation mismatch/wrong wirinq/insufficient qas
H7Fan motor overloaded/over current/sensor faultUHAnti freeze (other rooms)
H8AC current sensor error

McQuay SLM 3 – Inverter X Models air conditioner error codes

Error CodesFaulty Indication
E1Indoor temperature sensor loose / short
E2Outdoor temperature sensor loose / short
E3Communication error
E4Compressor overload protection
E5Pump fault
E6Compressor overheat / gas leak
E7IPM / PFC / Partial switching
E8Outdoor over current
E9Indoor fan feedback error

McQuay SLM 3-Netware 3 – Fan Coil Unit air conditioner error codes

1Indoor Sensor ErrorOFFOFFBLINK
2Indoor Pump ErrorOFFBLINKOFF
3Communication ErrorBLINKOFFOFF
4Outdoor Sensor ErrorOFFBLINKBLINK
5Compressor OverloadBLINKOFFOFF
6Pressure Switch TripBLINKOFFBLINK
7Pressure Sensor ErrorBLINKBLINKON

McQuay SLM 3-Netware 3-SLM 9 – On-Of air conditioner error codes

Error CodeFaulty Indication
E1Room air sensor contact loose / short
E2Indoor coil sensor contact open
E3Outdoor coil sensor contact open
E4Compressor overload protection/ Indoor coil sensor short/ Outdoor coil sensor short
E5Gas leak
E6Water Pump fault*
E7Outdoor coil sensor exist (Multi-split model)
E8Hardware error (tact switch pin short)
LORoom temperature below 8°C(46 °F)
HIRoom temperature above 37°C(99 °F)
OPWorking room sensor is open
SHWorking room sensor is short
HEAT LED blinkingDefrost mode (SLM3 only)