McQuay Air Conditioner Error Codes – Quick Solutions

Daikin Applied Americas formerly known as McQuay International is a company that designs, manufactures, and sells ventilation, heating, and air conditioners for commercial buildings. The company offers a wide range of products, systems, services, and parts that are ideal for your business needs. Purchased in Daikin Industries in 2006, McQuay became a subsidiary with headquarters in Minneapolis, Minnesota, USA.

While being a subsidiary the company offers products all over the world with the help of distributors and sales representatives. Focusing on its aim the company only offers the products it started with, but now its range includes systems that are suitable for home and commercial use.

McQuay might be a high-ranking company, but from time to time customers have complained about system errors. Fortunately, most of these errors can be fixed on your own. So rather than ignoring the error codes, your appliance is showing its time to note down the McQuay air conditioner error code and get to the bottom of the problem. To help you out we have listed down the most common error codes of McQuay air conditioners.

Codes List

Error CodesProblem
E1Compressor 2 low pressure faulty
E2Compressor 2 high pressure faulty
E3Compressor 2 overload
E4Indoor coil 2 temperature sensor fault
E5System 2 leaving water temperature 2 faulty
F2Indoor coil 1 temperature sensor fault
F4Return air temperature sensor fault
F6Communication faulty
F9Compressor  1 refrigerant leak
FECompressor 2 refrigerant leak
H1Compressor 1 overload
H4Compressor 1 high pressure faulty
L1Compressor 1 low pressure faulty
L3Temperature of water entering too high or low
L4Water flow switch faulty
L5System 1 leaving water temperature 1 faulty

Remote Control

McQuay Air Conditioner Remote Control
McQuay Air Conditioner Remote Control

Y Model Indoor Series Codes

Error CodesError Description
F6Heat exchanger overheat
U0Insufficient gas
H0Compressor sensor system abnormality
U2DC voltage out of range
H3High pressure switch error
U4Communication error
H6Position sensor abnormality
U7Signal transmission error (on outdoor unit PCB)
H8AC current sensor error
UAInstallation error
H9Outdoor air thermistor short / open
UFCommunication Error (indoor and outdoor) piping and wiring
J1Pressure sensor error
UHAnti-freeze function in other room
J3Compressor discharge pipe thermistor short /open / misplaced
A1Indoor PCB error
J5Suction pipe thermistor short/ open
A3Water pump error
J6Outdoor heat exchanger
J7Subcooling heat exchanger thermistor short/ open
A6Indoor fan motor abnormal
J8Liquid pipe thermistor short/ open
C4Indoor heat exchanger thermistor short/ open
J9Gas pipe thermistor abnormality
C9Indoor room thermistor short/ open
LCCommunication error (control PCB and inverter PCB)
L1Outdoor PCB error
L3Electrical box temperature rise
L4Heat sink overheat
E1Outdoor PCB error
E3High pressure protection
E4Low pressure protection
E5Compressor motor lock
L5IPM error / IGBT error
E6Compressor start-up error
L8Electrical thermal switch
E7Outdoor DC fan motor lock
L9Stall prevention
E8Ac input over current
P1Open phase or voltage unbalance
E9EXV error
P4Heat sink thermistor short / open
EA4-way valve error
PJCapacity setting error
F3Discharge pipe overheat

Wall Mounted K-Series Codes

McQuay AC Error Code Diagnosis
McQuay AC Error Code Diagnosis
Error CodesMeaning
UAIndoor-outdoor Unit Combination Fault
UORefrigerant Shortage
U2Drop Voltage Or Main Circuit Overvoltage
U4Failure Of Transmission (Between Indoor Unit And Outdoor Unit)
A1Indoor Pcb Defectiveness
A5High Pressure Control Or Freeze-up Protector
A6Fan Motor Fault
C4Faulty Heat Exchanger Temperature Sensor
C9Faulty Suction Air Temperature Sensor
EACooling-heating Switching Error
E1Circuit Board Fault
E5Ol Started
E6Faulty Compressor Start Up
E7Dc Fan Motor Fault
E8Overcurrent Input
F3High Temperature Discharge Ppe Control
F6High Pressrue Control (In Cooling)
H0Sensor Fault
H6Operation Fault Due To Faulty Position Detection Sensor
H8Dc Current Sensor Fault
H9Faulty Suction Air Temperature Sensor
J3Faulty Discharge Pipe Temperature Sensor
J6Faulty Heat Exchanger Temperature Sensor
L3Electrical Parts Heat Fault
L4High Temperature At Inverter Circuit Heatsink
L5Output Overcurrent
P4Faulty Inverter Circuit Heatsink Temperature Sensor

Error Diagnosis by Wired Controller (MC301)

McQuay Air Conditioner Remote Control Error Codes
McQuay Air Conditioner Remote Control Error Codes
Error MessagesMeaning
E0System malfunction
E1Sensor Broken (TH1 discharge Temp.)
E2Sensor Broken (TH2 inlet coil 1#)
E3Sensor Broken (TH3 mid coil 1#)
E4Sensor Broken (TH4 inlet coil 2#)
E5Sensor Broken (TH5 mid coil 2#)
E6Sensor Broken (TH6 inlet coil 3#)
E7Sensor Broken (TH7 mid coil 3#)
E8Sensor Broken (TH8 ambient temp)
E9Sensor Broken (TH9 outlet coil)
EASensor Broken (TH10 subcool outlet)
EBSensor Broken (TH11 subcool suction)
ECSensor Broken (TH12 suction)
EFEmergency Run
F0Outdoor Storage Malfunction
F1Sensor Broken (indoor inlet coil)
F2Sensor Broken (indoor mid coil)
F3Sensor Broken (indoor outlet coil)
F4Sensor Broken (indoor return air)
F5Sensor Broken (indoor supply air)
F6Indoor and controller communication malfunction
F7Ambient temp exceed the limit
F84WV malfunction
F9Refrigerant leakage
FAController storage malfunction
FBWater Pump (indoor water pump)
FCIndoor and outdoor communication malfunction
FEOutdoor master and slave communication malfunction
H0Digital comp overload
H1Fixed Comp1 overload
H2Fixed Comp2 overload
H3Fixed Comp3 overload
H4High pressure too high
H5Sensor broken, high pressure
H6Discharge temp too high
L0Super heat too low
L1Low pressure too low
L2Sensor broken, low pressure
10System malfunction
11Sensor broken (slave TH1 discharge temp)
12Sensor broken (slave TH2 inlet coil 1#)
13Sensor Broken (slave TH3 mid coil 1#)
14Sensor broken (slave TH4 inlet coil 2#)
15Sensor broken (slave TH5 mid coil 2#)
16Sensor broken (slave TH6 inlet coil 3#)
17Sensor broken (slave TH7 mid coil 3#)
18Sensor broken (slave TH8 ambient temp)
19Sensor broken (slave TH9 outlet coil)
1ASensor broken (slave TH10 subcool outlet)
1BSensor broken (slave TH11 subcool suction)
1CSensor Broken (slave TH12 suction)
1FEmergency run (slave)
20Outdoor storage (slave)
27Ambient temp exceed the limit (slave)
284WV malfunction (slave)
29Refrigerant leakage (slave)
30Digital comp overload (slave)
31Fixed comp1 overload (slave)
32Fixed comp2 overload (slave)
33Fixed comp 3 overload (slave)
34High pressure too high (slave)
35Sensor broken, high pressure (slave)
36Discharge temp too high (slave)
40Super heat too low (slave)
41Low pressure too low (slave)
42Sensor broken, low pressure (slave)

Cassette AC Codes

Mcquay Cassette AC Error Codes
Mcquay Cassette AC Error Codes

Wired Remote Control (Universal Board)

Display: E1 Blinking

Faulty Indication: Room sensor contact loose/ short

Display: E2 Blinking

Faulty Indication: Indoor coil sensor contact loose/ short

Display: E3 Blinking

Faulty Indication: Outdoor coil sensor contact loose/ short

Display: E4 Blinking

Faulty Indication: Compressor overload

Display: E5 Blinking

Faulty Indication: Gas leak

Display: E6 Blinking

Faulty Indication: Pump faulty

Display: Heat LED Blinking

Faulty Indication: Outdoor defrost (for Heatpump only)

Phase Sequencer
Phase Sequencer

PTAC Codes

McQuay PTAC Error Codes
McQuay PTAC Error Codes

Remote Controller Error Display:

E01: Room temperature sensor open. Automatically reset to restoration error.

E02: Room temperature sensor short. Automatically reset to restoration error.

E03: Error input from indoor unit or Outdoor unit.

McQuay PTAC Error Codes E1 - E35
McQuay PTAC Error Codes E1 – E35

Rooftop Package

McQuay Rooftop Package AC Error Codes
McQuay Rooftop Package AC Error Codes

When the system is on and an error occurs, the ON/OFF LED on the LCD panel will blink and an error code is shown. When the system is off and there is a thermistor error, the ON/OFF LED is off but the error code is still displayed. Each error code represents different message as below.

Error CodesPossible Fault
E01Require manual reset (possible causes)
E02Compressor 1 high temperature (overload)
E03Compressor 2 high temperature(overload)
E06Compressor 1 high pressure trip / contact open
E07Compressor 2 high pressure trip / contact open
E10Compressor 1 trip / low R-22 / outdoor abnormal
E11Compressor 2 trip / low R-22 / outdoor abnormal
E14Room sensor short
E15Room sensor open
E16Indoor coil sensor 1 short
E17Indoor coil sensor 2 short
E20Indoor coil sensor 1 open
E21Indoor coil sensor 2 open
E24Outdoor coil sensor 1 short
E25Outdoor coil sensor 2 short
E28 Outdoor coil sensor 1 open
E29Outdoor coil sensor 2 open
E32Compressor 1 de-ice
E33Compressor 2 de-ice
McQuay Rooftop Packaged Sequential Controller Functions


McQuay Rooftop Packaged AC Error Code
McQuay Rooftop Packaged AC Error Codes


When a malfunction of the air conditioner unit is detected, immediately switch off the main power supply before proceeding with the following troubleshooting procedures.

The following are common fault conditions and simple troubleshooting tips. If any other fault conditions which are not listed occur, contact your nearest local dealer. DO NOT attempt to troubleshoot the unit by yourself.

Fault ConditionPossible Cause
The air conditioner unit will not resume after power failure.The auto restart function is not functioning. Please turn on the unit with the wireless / wired controller.
The airfl ow is too slow or room cannot be cooled suffi ciently.
  • The air filter is dirty.

  • The doors and windows are opened.

  • The air suction and discharge of both indoor and outdoor units are clogged or blocked.

  • The regulated temperature or temperature setting is not low enough

  • Discharge airfl ow has bad odor.
  • Cigarettes, smoke particles, perfume and others, which might have adhered onto the coil, may cause odor.

  • Contact your nearest dealer

  • Condensation on the front air grille of the indoor unit.
  • This is caused by air humidity after an extended period of operation.

  • The set temperature is too low. Increase the temperature setting and operate the unit at high fan speed

  • Water fl owing out from the air conditioner.Switch off the unit and contact your nearest dealer. This might be due to tilted installation.
    Hissing airfl ow sound from the air conditioner unit during operation.Liquid refrigerant fl owing into the evaporator coil.
    The wireless controller display is dim.
  • The batteries are discharged.

  • The batteries are not correctly inserted.

  • The assembly is not good.

  • Compressor operates continuously.
  • Dirty air fi lter. Clean the air fi lter.

  • Temperature setting too low (cooling). Use higher temperature setting.

  • Temperature setting too high (heating), Use lower temperature setting.

  • No cool air comes out during cooling cycle, or no hot air comes out during heating cycle.
  • • Temperature setting too high (cooling). Use lower temperature setting.

  • • Temperature setting too low (heating). Use higher temperature setting.

  • On heating cycle, warm air does not come out.Unit is in defrost mode. Heating operation will resume after defrost cycle ends.

    LED Indicator Lights

    Normal Operation and Fault Conditions for Heat Pump Unit

    McQuay AC LED Indicator Lights
    McQuay AC LED Indicator Lights

    Manuals Pdf

    McQuay Air Conditioning Manual PDF

    Mcquay Cassette AC MANUAL PDF

    McQuay Rooftop Packaged AC Manual PDF

    *If you can't find the code you're looking for on our site, please let us know, and we'll update our database as soon as possible.

    19 thoughts on “McQuay Air Conditioner Error Codes – Quick Solutions”

    1. Maaf saya mau bertanya.AC mc quai 40Pk posisi di startup pake thermostat nyala trus pas ketika di matikan pake thermostat masih tetap menyala kenapa kira kira permasalahaan nya?


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