Mitsubishi City Multi air conditioner fault codes

The fault code check list below will give you an idea of what is going on with your Mitsubishi City Multi air conditioning system. Each fault code has a brief description, which will let you understand how serious the problem is. This is an easy-to-use and quick reference guide.
Of course, finding out what the fault code means is just the first step, but it will give you an idea of the issue. It may well happen that you will not be able to solve the problem on your own, so you will have to call technical support and book an engineer. In this case we recommend that you write down the Mitsubishi City Multi error code and tell this number to the tech support.

Mitsubishi City Multi AC fault codes

FAULT
CODE
R22R4O7cR410ALOSSNAYDESCRIPTION
403xxx-Comms fault between boards - check inverter error detail for which 2 boards,
check transformer , bus voltage and inter-connecting cables
900----Lossnay unit in test run
1102xxx-High compressor discharge temperature. Discharge temperature has exceeded
110°C or more. Short of refrigerant. Discharge thermistor
1111xx--Low pressure/temperature fault - check thermistors (TH2, TH3, TH4), gas charge,
indoor fan, heat exchanger and filter
1112xx--Low pressure/temperature fault - check thermistors (TH2, TH3, TH4), gas charge,
indoor fan, heat exchanger and filter
1113xx--Low pressure/temperature fault - check thermistors (TH2, TH3, TH4), gas charge,
indoor fan, heat exchanger and filter
1202xxx-Preliminary fault to 1102
1204--x-Preliminary heat exchanger gas temperature sensor fault - check thermistors 10a and 10b
1205xxx-Preliminary thermistor fault (TH5)
1211xx--Preliminary thermistor fault (TH2)
1214xxx-Preliminary thermistor fault (THHS)
1216xxx-Preliminary thermistor fault (TH7)
1217xxx-Preliminary thermistor fault (TH8)
1219xx--Preliminary thermistor fault (TH9)
1221xxx-Preliminary thermistor fault (TH6)
1243-x--Preliminary thermistor fault (TH10)
1301-x--Low pressure fault (63L operation) low pressure sensor sensing less
than 1 bar immediately before starting
1302xx--High pressure fault - check pressure in system for more than 29 bar (R407c)
38 bar (R410A). Check high pressure sensor against gauge pressure
1368xx--Pressure sensor fault (PS1) at BC - compare pressure reading on SW1 on O/C
1370xx--Pressure sensor fault (PS3) at BC - compare pressure reading on SW1 at O/C
1402--x-Preliminary fault to 1302
1500xxx-System overcharge. Abnormal low compressor superheat - discharge thermistor TH4
1501xx--High compressor shell temp - check for shortage of gas, insufficient indoor
index running (comms room units)
1505xx--Suction pressure abnormal - generated by low pressure sensor detecting a
vacuum - check for blockage, closed valve or sensor fault
2500xxx-Detecting lack of water flow on a water circuit
2502xxx-I/C has water level in drip tray, when the unit was running in cooling
(temperature sensors - check for open or closed circuit and operation of pump)
2503xxx-I/C has water level in drip tray when the unit was running in cooling
(float sensor - check for closed circuit on float switch and operation of pump)
2600x-x-Water leak from humidifier
4100----Compressor over current protection on Mr Slim with M-net interface -
check inverter or compressor
4101----Compressor over current protection on Mr Slim with M-net interface -
check inverter or compressor
4102--x-Open phase fault - check power supply and noise filter for loss of phase,
check wiring and fuses
4103xxx-Reverse phase fault - check phase rotation, loss of phase through the noise filter ,
fuse blown and high pressure switch open at power on
4106--x-Transmission power supply fault - check wiring, high current, incorrect voltage
on transmission line and/or M-Net board
4108-x--Over current protection on DOL compressor - check power supply,
contactor and compressor
4115xxx-Power supply abnormal - check power , fuses, connections and PCB
4116xxx-Fan motor abnormal - check fan motor and board (relates to indoor unit or Lossnay unit)
4124----Thermal switch (49C) open circuit on Mr Slim on M-Net - reset and check
pressures and air flow
4210x---Compressor over current problem - check inverter balance. Compressor and inverter
4220-xx-Low inverter board BUS voltage. Less than 289VdcDC is detected. - check mains supply
4225--x-Low DC voltage on Vdc on fan inverter - check CNVdc for 300Vdc on diode stack
and check mains power supply to outdoor unit
4230xxx-High temperature on heat sink on inverter - check for blockages in air duct,
failure of INV fan or failure of thermistor
4235--x-Fan inverter heat sink overheat protection. Reduced airflow through heat sink.
Fan motor problem. THHS thermistor problem.
4240xxx-Over current protection. If high current is detected for more than 10 minutes -
check inverter balance. Reduced airflow through heat sink
4245--x-Over current protection. Possible ACCT current sensor fault.
Should read 280 ohms between pins 1 & 2 and across pins 3 & 4
4250--x-Over current protection. Inverter IPM problem. Compressor lock - check inverter balance
4255--x-Inverter cooling fan problem - if high static fan is used then check that SW3-9 is on
4260-xx-Preliminary inverter heat sink overheat protection. Reduced airflow through
heat sink. Fan motor problem. THHS thermistor problem.
5101xxx-Thermistor fault at indoor/outdoor unit - check fault code address
5102xxx-Thermistor fault at indoor/outdoor unit - check fault code address
5103xxx-Thermistor fault at indoor/outdoor unit - check fault code address
5104xxx-Thermistor fault at indoor/outdoor unit - check fault code address
(indoor fault - check SW7-3 is off)
5105xxx-TH5 open/short circuit - check if the TH is disconnected from the board
5106xxx-TH6 open/short circuit - check if the TH is disconnected from the board
5107xxx-TH7 open/short circuit - check if the TH is disconnected from the board
5108xx--TH8 open/short circuit - check if the TH is disconnected from the board
5109-x--TH9 open/short circuit - check if the TH is disconnected from the board
5110xxx-TH10 open/short circuit - check if the TH is disconnected from the board
5111x-x-BC box thermistor error - TH11 open/short circuit, disconnected from board/pipe
5112xxx-BC box thermistor error - TH10 open/short circuit, disconnected from board/pipe
5113x---BC box thermistor error - TH open/short circuit, disconnected from board/pipe
5114x---BC box thermistor error - TH open/short circuit, disconnected from board/pipe
5115x-x-BC box thermistor error - TH15 open/short circuit, disconnected from board/pipe
5116x-x-BC box thermistor error - TH16 open/short circuit, disconnected from board/pipe
5201xxx-Pressure sensor fault outdoor unit/BC box - check fault code address/SW1
pressure sensor readings
5202x---Pressure sensor fault (PS2) in the BC box
5203xxx-Pressure sensor fault (PS3) in the BC box
5300----A-Control UH fault - see Mr Slim fault code list
5301-xx-Current sensor fault, ACCT or DCCT - check inv. error details
5401--x-Temperature sensor fault - check CN30 for humidity sensor
5701--x-Loose float switch connector - check switch, check CN4F on indoor unit
6201--x-TB7 transmission line communication error - check for voltage abnormality/short
6202--x-Transmission processor hardware error - check for noise/short on M-Net cable
6600xxx-Repeat address fault - two or more units are assigned the same address -
correct the repeated address
6601--x-Polarity setting error - no voltage or short circuit on the m-net transmission line
6602xxx-Hardware error of transmission processor . Noise interference. Polarity problem on TB7
6603xxx-Bus circuit busy - check if indoor unit, Lossnay unit or anything else has been wired
into TB7, instead of TB3
6607xxx-Communication issue - no response back from unit whilst system is operational
6608xxx-Communication error - loss of voltage or noise entering the transmission line
6700----K control communication error - R22 type unit connected onto M-Net circuit comms error
6701----K control communication error - R22 type unit connected onto M-Net circuit comms error
6702----K control duplicate address error - two or more R22 type units connected onto
M-Net circuit with the same address
6750----K control communication error - R22 type unit connected onto M-Net circuit comms error
6751----R22 R/A thermistor fault (P1)
6752----R22 frost protection at I/C (P6)
6753----Comms fault between O/C and I/C
6754----R22 drain fault (P5)
6755----R22 drain fault (P5)
6756----R22 frost protection at I/C (P6)
6757----System error
6758----Comms fault between I/C and O/C
6761----R22 R/A thermistor fault (P1)
6762----R22 TH2 fault check resistance (P2)
6763----R22 Comms fault between I/C and O/C
6764----R22 drain fault (P4)
6765----R22 drain fault (P5)
6766----R22 frost protection at I/C (P6)
6767----R22 comms fault between I/C and O/C
6771----K abnormality - high pressure abnormality or low pressure abnormality
6772----K abnormality - inner thermostat function, discharge temperature abnormality,
shell thermostat function, over current protection
6773----K abnormality - radiator plate thermostat function
6774----K abnormality - outdoor thermistor abnormality
6775----K abnormality - pressure sensor abnormality, indoor/outdoor communication error
6776----K abnormality - over current shut-off
6777----K abnormality - system error
6778----K abnormality - normal
6779----K abnormality - refrigerant overcharge, abnormal voltage, abnormal CT sensor
6830----Comms fault between I/C and R/C check connections to MA R/C and check for
12Vdc check R/C not set sub controller
6831--x-MA R/C communication fault - check connections on TB15 or that the controller
was removed while the I/C was powered
6832-x-MA controller comms fault - check cable length no bigger than 500m, check
connection and type of cable used, check R/C not set sub on field settings
6833--x-MA controller comms fault check cable length no bigger than 500m, check
connection and type of cable used, check R/C not set sub on field settings
6834--x-MA Controller comms fault - check cable length no bigger than 500m,
check connection and type of cable used, check R/C not set sub on field settings
6840----A-Control E6/E8 fault - see Mr Slim fault code list
6841----A-Control E7/E9 fault - see Mr Slim fault code list
6844----A-Control EA fault - see Mr Slim fault code list
6845----A-Control Eb fault - see Mr Slim fault code list
6846----A-Control EC fault - see Mr Slim fault code list
7100xxx-Over capacity - (R2 150% index exceeded) (Y 130% index exceeded)
7101xxx-Capacity setting error - SW2 set wrong on indoors, SW5 on YHMA outdoor ,
(SW3-10 on older kit)
7102xxx-Error in number of connected units - loss of M-Net voltage (short or break),
no power to BC, wrong SW5 setting on box, wrong box type
7105xxx-Address setting error - OC or BC addressed wrong
7106-xx-Attribute setting error - SW3-1 setting on a GUF
7107xxx-Port setting error - check if too much capacity on a single port, wiring SW2 setting,
wrong SW14 setting or wrong units on a box when using multiple boxes
7110--x-Check SW5-7 is correctly set
7111xxx-Remote control sensor fault - SW1 - 1 on and no controllers fitted or faulty
remote controller
7113--x-Function setting error - wrong SW5 setting or wrong resistors fitted on YHM-A
7117--x-Model setting error - SW5 set wrong or wrong resistors in
7130-xx-Incompatible equipment on M-Net - check split with MAC 399 wired onto the TB5 line
TB5 line, not the TB7